KR101758548B1 - Gallium nitride self-supported substrate, light-emitting device and manufacturing method therefor - Google Patents

Abstract

There is provided a gallium nitride self-standing substrate made of a plate composed of a plurality of gallium nitride single crystal particles having a single crystal structure in a direction of a normal line. This gallium nitride self-supporting substrate includes a step of preparing an oriented polycrystalline sintered body, a step of forming a seed crystal layer of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body, Forming a layer made of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer; removing the oriented polycrystalline sintered body to obtain a gallium nitride self- Or a process comprising the steps of: INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a gallium nitride self-supporting substrate useful as a substitute material for a gallium nitride monocrystalline substrate, which is inexpensive and suitable for large area.

Description

TECHNICAL FIELD [0001] The present invention relates to a gallium nitride self-supporting substrate, a light emitting device, and a method of manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a gallium nitride self-supporting substrate, a light emitting device, and a method of manufacturing the same.

As a light emitting device such as a light emitting diode (LED) using a single crystal substrate, it is known that various gallium nitride (GaN) layers are formed on sapphire (a-alumina single crystal). For example, a structure in which a multi quantum well layer (MQW) in which an n-type GaN layer, a quantum well layer made of an InGaN layer and a barrier layer made of a GaN layer are alternately stacked, and a p-type GaN layer are sequentially laminated is formed on a sapphire substrate Have been mass-produced. A laminated substrate suitable for such use has also been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. H06-184144 proposes a gallium nitride crystal laminated substrate comprising a sapphire base substrate and a gallium nitride crystal layer formed by crystal growth on the substrate.

However, when a GaN layer is formed on a sapphire substrate, the GaN layer tends to cause dislocation because the lattice constant and the thermal expansion rate do not coincide with sapphire, which is a heterogeneous substrate. Further, since sapphire is an insulating material, an electrode can not be formed on its surface, and therefore, a vertical-structured light-emitting element having electrodes on the front and back of the element can not be formed. Therefore, an LED in which various GaN layers are formed on a gallium nitride (GaN) single crystal attracts attention. GaN single crystal substrate is a material of the same kind as the GaN layer, so that the lattice constant and the thermal expansion coefficient are easily matched, and a performance improvement can be expected as compared with the case of using a sapphire substrate. For example, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2010-132556) discloses an independent n-type gallium nitride monocrystalline substrate having a thickness of 200 μm or more.

Japanese Patent Application Laid-Open No. 12-184144 Japanese Patent Application Laid-Open No. 2010-132556

However, the monocrystalline substrate generally has a small area and is expensive. Particularly, it is required to reduce the manufacturing cost of LEDs using a large-area substrate, but it is not easy to mass-produce a large-sized monocrystalline substrate, and the manufacturing cost is higher. Therefore, an inexpensive material which can be a substitute material for a single crystal substrate such as gallium nitride is required.

The inventors of the present invention have obtained the knowledge that it is now possible to fabricate a gallium nitride self-supporting substrate which is inexpensive and suitable for large-area fabrication, as a substitute material for a gallium nitride single crystal substrate.

Therefore, an object of the present invention is to provide a gallium nitride self-supporting substrate useful as a substitute material for a gallium nitride monocrystalline substrate, which is inexpensive and also suitable for large area.

According to one aspect of the present invention, there is provided a gallium nitride self-standing substrate comprising a plate composed of a plurality of gallium nitride-based single crystal particles having a single crystal structure in a normal direction.

According to another aspect of the present invention, there is provided a GaN self-

Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains formed on the substrate and having a single crystal structure in a substantially normal direction,

Emitting layer.

According to still another aspect of the present invention, there is provided a method of manufacturing an aligned polycrystalline sintered body,

Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body;

Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer;

A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-

The method comprising the steps of:

According to still another aspect of the present invention, there is provided a method of manufacturing a gallium nitride self-sustaining substrate, comprising the steps of: preparing a gallium nitride self-supporting substrate according to the present invention;

At least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a substantially normal direction is formed on the gallium nitride free-standing substrate so as to have a crystal orientation substantially corresponding to the crystal orientation of the gallium nitride substrate, fair

And a light emitting device.

In particular, according to the present invention, the following preferred embodiments are provided.

[Item 1] A gallium nitride self-supporting substrate comprising a plate composed of a plurality of gallium nitride single crystal grains having a single crystal structure in a normal direction, wherein the gallium nitride single crystal grains exposed on the surface of the gallium nitride self- Sectional area average diameter D _B on the outermost surface of the gallium nitride single crystal particles exposed on the back surface of the gallium nitride self-supporting substrate, the gallium nitride self- Wherein a ratio (D _T / D _B ) of a cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the self-supporting substrate is larger than 1.0.

[Item 2] The gallium nitride self-standing substrate according to item 1, wherein the average diameter of the cross-section of the gallium nitride single crystal particles on the outermost surface of the substrate is 0.3 μm or more.

[Item 3] The gallium nitride self-standing substrate according to item 2, wherein the cross-sectional average diameter is 3 占 퐉 or more.

[Item 4] The gallium nitride self-standing substrate according to item 2, wherein the cross-sectional average diameter is 20 m or more.

[Item 5] A gallium nitride self-standing substrate according to any one of items 1 to 4, having a thickness of 20 m or more.

[Item 6] The GaN self-standing substrate according to any one of Items 1 to 5, having a size of 100 mm or more in diameter.

[Item 7] The gallium nitride self-standing substrate according to any one of items 1 to 6, wherein the gallium nitride monocrystalline grains have a crystal orientation substantially aligned in the normal direction.

[Item 8] The gallium nitride self-standing substrate according to any one of items 1 to 7, wherein the gallium nitride single crystal particle is doped with an n-type dopant or a p-type dopant.

[Item 9] The gallium nitride self-standing substrate according to any one of items 1 to 7, wherein the gallium nitride single crystal particle does not contain a dopant.

[Item 10] The gallium nitride self-standing substrate according to any one of items 1 to 9, wherein the gallium nitride single crystal particles are mixed.

[Section 11] The ratio (D _T / D _B) of 1.5 or more, a self-standing gallium nitride substrate according to any one of claims 1 to 10 wherein.

[Item 12] An aspect ratio, defined as a ratio of the thickness T of the gallium nitride self-supporting substrate to the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride self- (T / D _T ) of the GaN substrate is 0.7 or more.

[Item 13] A GaN self-supporting substrate according to any one of Items 1 to 12,

Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains formed on the substrate and having a single crystal structure in a substantially normal direction,

Emitting device.

[Item 14] The self-supporting light-emitting device according to item 13, wherein the semiconductor monocrystalline particles on the outermost surface of the light-emitting functional layer have an average cross-sectional diameter of 0.3 m or more.

[Item 15] The light-emitting device according to item 14, wherein the cross-sectional average diameter is 3 占 퐉 or more.

[Item 16] A light-emitting device according to any one of items 13 to 15, wherein the semiconductor single crystal grains have a structure in which the crystal orientation of the gallium nitride self-supporting substrate is substantially grown.

[Item 17] A light-emitting device according to any one of items 13 to 16, wherein the light-emitting functional layer is made of a gallium nitride-based material.

[Item 18] A method for manufacturing a semiconductor device, comprising the steps of: preparing an oriented polycrystalline sintered body;

Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body;

Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer;

A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-

Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride free standing substrate are communicated with the back surface of the gallium nitride free standing substrate without passing through grain boundaries and are exposed on the back surface of the gallium nitride free standing substrate Sectional area average diameter D _T on the outermost surface of the gallium nitride single crystal particle exposed on the surface of the gallium nitride independent substrate with respect to the cross-sectional average diameter D _B on the outermost surface of the present gallium nitride single crystal grain D _T / D _B ) is greater than 1.0.

[Item 19] The method according to item 18, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body.

[Item 20] The method according to item 18 or 19, wherein the average particle size of the particles constituting the oriented polycrystalline sintered body is 0.3 to 1000 탆.

[Item 21] The method according to any one of items 18 to 20, wherein the layer composed of the gallium nitride crystal is formed by the Na flux method.

[Item 22] The method according to any one of items 18 to 21, wherein the oriented polycrystalline sintered body has translucency.

Preparing a gallium nitride self-supporting substrate according to any one of items 1 to 12, or preparing the gallium nitride self-supporting substrate according to any one of items 18 to 22,

At least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a substantially normal direction is formed on the gallium nitride free-standing substrate so as to have a crystal orientation substantially corresponding to the crystal orientation of the gallium nitride substrate, fair

Emitting device.

[Item 24] The method according to item 23, wherein the light-emitting functional layer is made of a gallium nitride-based material.

[Item 25] A gallium nitride self-supporting substrate comprising a plate composed of a plurality of gallium nitride monocrystalline grains having a single crystal structure in a normal direction, wherein the gallium nitride monocrystalline grains exposed on the surface of the gallium nitride self- Wherein the gallium nitride monocrystalline grain on the outermost surface of the substrate is not less than 20 占 퐉 and not more than 1000 占 퐉.

[Item 26] A gallium nitride self-standing substrate according to item 25, wherein the cross-sectional average diameter is 50 占 퐉 or more and 500 占 퐉 or less.

[Item 27] A gallium nitride self-standing substrate according to item 25 or 26, having a thickness of 20 m or more.

[Item 28] A gallium nitride self-standing substrate according to any one of items 25 to 27, having a size of 100 mm or more in diameter.

[Item 29] The gallium nitride self-standing substrate according to any one of items 25 to 28, wherein the gallium nitride monocrystalline grains have a crystal orientation substantially aligned in the normal direction.

[Item 30] The gallium nitride self-standing substrate according to any one of items 25 to 29, wherein the gallium nitride single crystal particle is doped with an n-type dopant or a p-type dopant.

[Item 31] The gallium nitride self-standing substrate according to any one of items 25 to 29, wherein the gallium nitride single crystal particle does not contain a dopant.

[Item 32] A gallium nitride self-standing substrate according to any one of items 25 to 31, wherein the gallium nitride single crystal particles are mixed.

[Item 33] A method for producing gallium nitride single crystal particles, wherein the gallium nitride single crystal particles exposed on the back surface of the gallium nitride single crystal substrate have a cross-sectional average diameter D _B on the outermost surface of the gallium nitride single crystal particles, 32. The gallium nitride self-standing substrate according to any one of items 25 to 32, wherein a ratio (D _T / D _B ) of a cross-sectional average diameter D _{T on} the surface is larger than 1.0.

[Item 34] An aspect ratio ratio defined as a ratio of the thickness T of the gallium nitride self-supporting substrate to the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride self- (T / D _T ) of the GaN substrate is 0.7 or more.

[Item 35] The gallium nitride self-standing substrate described in any one of items 25 to 34,

Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains formed on the substrate and having a single crystal structure in a substantially normal direction,

Emitting device.

[Item 36] The self-supported light-emitting device according to Item 35, wherein the semiconductor monocrystalline particles on the outermost surface of the light-emitting functional layer have an average cross-sectional area of 20 mu m or more.

[Item 37] The light-emitting device according to item 36, wherein the cross-sectional average diameter is 50 占 퐉 or more.

[Item 38] The light emitting device according to any one of items 35 to 37, wherein the semiconductor single crystal particles have a structure in which the crystal orientation of the gallium nitride self-supporting substrate is substantially grown.

[Item 39] The light-emitting element described in any one of items 35 to 38, wherein the light-emitting functional layer is made of a gallium nitride-based material.

A method for manufacturing a sintered body,

Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body;

Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer;

A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-

Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride free standing substrate are connected to the back surface of the gallium nitride free standing substrate without passing through grain boundaries, Wherein the single-crystal single-crystal grains have a cross-sectional average diameter of 20 mu m or more and 1000 mu m or less.

[Item 41] The method according to item 40, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body.

[Item 42] The method according to item 40 or 41, wherein the average particle size of the particles constituting the oriented polycrystalline sintered body is 0.3 to 1000 탆.

[Item 43] A method according to any one of items 40 to 42, wherein the layer composed of the gallium nitride crystal is formed by the Na flux method.

[Item 44] The method according to any one of items 40 to 43, wherein the oriented polycrystalline sintered body has translucency.

[45] A process for producing a gallium nitride self-standing substrate according to any one of items 25 to 34, or a method for manufacturing a gallium nitride self-standing substrate according to any one of items 40 to 44,

At least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a substantially normal direction is formed on the gallium nitride free-standing substrate so as to have a crystal orientation substantially corresponding to the crystal orientation of the gallium nitride substrate, fair

Emitting device.

[Item 46] The method according to item 45, wherein the luminescent functional layer is composed of a gallium nitride-based material.

1 is a schematic cross-sectional view showing an example of a vertical type light emitting device manufactured using the gallium nitride self-supporting substrate of the present invention.
Fig. 2 is a reverse polar plot of the cross-section of the gallium nitride crystal measured in Example 4. Fig.
Fig. 3 is an inverse pole-point bearing mapping of the plate surface (surface) of the gallium nitride crystal measured in Example 4. Fig.
Fig. 4 is a crystal mapping in the vicinity of the interface between the gallium nitride crystal and the oriented alumina substrate measured in Example 4. Fig.
Fig. 5 is a conceptual diagram of the growth behavior of gallium nitride crystals discussed in Examples 4 and 5. Fig.
6 is an inverse pole-point orientation mapping of the cross section of the gallium nitride crystal measured in Example 5. Fig.

Gallium nitride  Self-supporting substrate

The gallium nitride substrate of the present invention may have the form of a self-supporting substrate. In the present invention, the term " self-supporting substrate " means a substrate that can be handled as a solid without being deformed or broken by its own weight when handled. The gallium nitride self-standing substrate of the present invention can be used as a substrate of various semiconductor devices such as a light emitting device. In addition to this, a substrate other than a substrate such as an electrode (which may be a p-type electrode or an n-type electrode), a p- Layer. On the other hand, in the following description, the advantages of the present invention are described by exemplifying a light emitting element which is one of main applications, but the same or similar advantages can be applied to other semiconductor devices within a range that does not impair technical consistency.

The gallium nitride free standing substrate of the present invention comprises a plate composed of a plurality of gallium nitride single crystal grains having a single crystal structure in a direction of a normal line. That is, the gallium nitride self-sustaining substrate is composed of a plurality of semiconductor single crystal grains two-dimensionally connected in the horizontal plane direction, and therefore has a single crystal structure in a substantially normal direction. Therefore, the gallium nitride self-supporting substrate is not a single crystal as a whole but has a single crystal structure in a local domain unit, so that it can have high crystallinity enough to secure device characteristics such as a light emitting function. However, the gallium nitride self-standing substrate of the present invention is not a single crystal substrate. As described above, a single crystal substrate generally has a small area and is expensive. Particularly, in recent years, it is required to reduce the cost of manufacturing LEDs using a large area substrate, but it is not easy to mass-produce a large-area single crystal substrate, and the manufacturing cost is higher. These drawbacks are solved by the gallium nitride self-supporting substrate of the present invention. That is, according to the present invention, it is possible to provide a gallium nitride self-supporting substrate useful as a substitute material for a gallium nitride monocrystalline substrate, which is inexpensive and suitable for enlargement. Further, by using gallium nitride which is made conductive by the introduction of the p-type or n-type dopant as the substrate, it is possible to realize a vertical-structured light-emitting device, thereby increasing the luminance. In addition, a large-area surface emitting element used for surface emitting illumination or the like can be realized at low cost. Particularly, when the vertical LED structure is manufactured using the gallium nitride self-supporting substrate of the present invention, since the plurality of gallium nitride single crystal grains constituting the self-supporting substrate have a single crystal structure in the normal direction, No system exists, and as a result, a desirable luminous efficiency is expected. In this respect, in the case of an oriented polycrystalline substrate having a grain boundary in the normal direction, there is a possibility that the luminous efficiency is lowered because a high-resistance grain boundary exists on the current path even in the vertical type structure. From these viewpoints, the gallium nitride self-standing substrate of the present invention can be suitably used for a vertical LED structure.

Preferably, the plurality of gallium nitride-based single crystal grains constituting the self-supporting substrate have a crystal orientation oriented substantially in the normal direction. The term " substantially oriented crystal orientation in the direction of the normal line " is not necessarily a crystal orientation that is perfectly aligned in the normal direction. As long as a device such as a light emitting device using a self- It means that the crystal orientation should be somewhat aligned in a similar direction. It can also be said that the gallium nitride single crystal grain has a structure in which the crystal orientation of the oriented polycrystalline sintered body used as the base substrate is grown substantially in accordance with the production method. The term " structure in which the crystal orientation of the oriented polycrystalline sintered body is substantially grown " means a structure in which crystal growth is influenced by the crystal orientation of the oriented polycrystalline sintered body and is necessarily a structure in which the crystal orientation of the oriented polycrystalline sintered body is completely grown And the crystal orientation of the oriented polycrystalline sintered body may be grown to some extent as long as device characteristics such as a light emitting device using a self-supporting substrate can secure desired device characteristics. That is, this structure also includes a structure that grows in a crystal orientation different from that of the oriented polycrystalline sintered body. In that sense, the expression " a structure grown substantially along a crystal orientation " may be said to be a " structure grown largely from a crystal orientation ", and this phrase and the same meaning apply to the same expression in the present specification . Therefore, such crystal growth is preferably performed by epitaxial growth, but the present invention is not limited to this, and various crystal growth types similar thereto may be used. Whatever the case, by growing in this way, the gallium nitride self-supporting substrate can have a structure in which the crystal orientation is substantially aligned with respect to the normal direction.

Therefore, it is possible to grasp that the gallium nitride self-supporting substrate is an aggregate of gallium nitride single crystal particles having a columnar structure in which the grain boundary is observed when viewed in the normal direction and viewed in the single crystal in the horizontal plane direction. Here, the " columnar structure " does not only mean a typical vertically long columnar shape but also a meaning including various shapes such as a horizontally elongated shape, a trapezoidal shape, and a trapezoidal inverted shape . However, as described above, the gallium nitride free-standing substrate has a structure having a crystal orientation somewhat aligned with a direction normal to the normal direction, and it is not necessarily a columnar structure in a strict sense. It is considered that the cause of the columnar structure is that the gallium nitride single crystal grain grows under the influence of the crystal orientation of the oriented polycrystalline sintered body used for manufacturing the gallium nitride self-supporting substrate, as described above. For this reason, it is considered that the average grain size (hereinafter referred to as the average cross-sectional diameter) of the cross section of the gallium nitride single crystal grain, which may be referred to as the pillar structure, depends not only on the film forming conditions but also on the average grain size of the surface of the oriented polycrystalline sintered body. In the case where the gallium nitride self-supporting substrate is used as a part of the light-emitting functional layer of the light emitting device, the light transmittance in the cross-directional direction is deteriorated due to the presence of the grain boundary, and the light is scattered or reflected. Therefore, in the case of a light emitting device having a structure for extracting light in the normal direction, an effect of increasing brightness by scattered light from grain boundaries is also expected.

As described above, in the vertical LED structure using the gallium nitride self-sustaining substrate of the present invention, the self-supporting substrate surface on which the light-emitting functional layer is to be formed and the back surface of the self-supporting substrate on which the electrodes are to be formed, . That is, it is preferable that the gallium nitride single crystal particles exposed on the surface of the gallium nitride self-supporting substrate communicate with the back surface of the gallium nitride self-supporting substrate without passing through the grain boundaries. If the grain boundary exists, it causes resistance to the display, which causes a decrease in luminous efficiency.

However, in the case of growing gallium nitride crystal by epitaxial growth through vapor phase or liquid phase, growth may occur not only in the normal direction but also in the horizontal direction, depending on the deposition conditions. At this time, if there is a change in the quality of the grain as the starting point of growth and the quality of the final definition made thereon, the growth rate of the individual gallium nitride crystal is different. For example, as shown in FIG. 5, It may grow in such a way as to cover slow particles. When this growth behavior is taken, the particles on the substrate surface side are more likely to be hardened by substitution than the substrate backside. In this case, crystals having a slow growth are stopped on the way of growth, and the grain boundary can be observed in the normal direction as viewed from any one end face. However, the particles exposed on the surface of the substrate are communicated with the back surface of the substrate without passing through the grain boundaries, and there is no low (resistance phase) in current flow. In other words, after the formation of the gallium nitride crystal, the particles exposed on the substrate surface side (opposite to the side where the substrate is in contact with the oriented polycrystalline sintered body at the time of manufacturing) are predominantly particles communicating with the back surface , It is preferable to fabricate the light-emitting functional layer on the substrate surface side from the viewpoint of increasing the luminous efficiency of the vertical-structured LED. On the other hand, since the backside of the substrate (the side which was in contact with the oriented polycrystalline sintered body as the base substrate at the time of manufacturing) also contains particles that do not communicate with the substrate surface side (see, for example, FIG. 5) There is a possibility that the light emitting efficiency is lowered. In addition, as described above, in the case of such a growth behavior, the large-size gallium nitride free-standing substrate is referred to as the substrate front surface side and the small one is the substrate back surface side I can tell. That is, in the GaN self-supporting substrate, it is preferable to fabricate the light-emitting functional layer on the side where the grain diameter of the gallium nitride crystal is large (toward the front surface of the substrate) from the viewpoint of enhancing the luminous efficiency of the vertical-structured LED. On the other hand, in the case of using the oriented polycrystalline alumina sintered body oriented in the c-plane or the like on the base substrate, the surface of the substrate (opposite to the side in contact with the oriented polycrystalline alumina sintered body, The side which had been in contact with the oriented polycrystalline alumina sintered body as the base substrate) became a nitrogen surface. That is, the gallium surface of the gallium nitride self-supporting substrate is predominantly in contact with the back surface of the substrate without passing through the grain boundary. Therefore, from the viewpoint of increasing the luminous efficiency of the vertical-structured LED, it is preferable to fabricate the light-emitting functional layer on the gallium surface side (substrate front surface side).

Therefore, when the grain growth on the substrate surface side is larger than that on the substrate backside side, that is, when the gallium nitride single crystal grain exposed on the substrate surface has a cross-sectional average diameter larger than that of the gallium nitride system (It is preferable that the number of the gallium nitride single crystal particles exposed on the substrate surface is smaller than the number of the gallium nitride single crystal grains exposed on the back surface of the substrate It may be said that it is preferable). Concretely, the ratio of the average cross-sectional average diameter (hereinafter referred to as the cross-sectional average diameter D _B of the back surface of the substrate) of the gallium nitride single crystal grains exposed on the back surface of the gallium nitride self- (D _T / D _B ) of the average cross-sectional average diameter (hereinafter referred to as the cross-sectional average diameter D _T of the substrate surface) of the outermost surface of the gallium nitride monocrystalline grains exposed on the surface is preferably larger than 1.0, More preferably not less than 1.5, still more preferably not less than 2.0, particularly preferably not less than 3.0, and most preferably not less than 5.0. However, if the ratio (D _T / D _B ) is too high, the light emitting efficiency may be lowered inversely. Therefore, it is preferably 20 or less, more preferably 10 or less. The reason why the luminous efficiency is changed is not clear. However, it is considered that when the ratio (D _T / D _B ) is high, the grain boundary area which does not contribute to light emission by the substitution hardening is decreased or the substitution hardening is reduced . The reason why the crystal defects are reduced is not clear, but it is also considered that the particles containing defects grow slowly and the particles with few defects grow at high speed. On the other hand, if the ratio (D _T / D _B ) is too high, the particles communicating between the substrate surface and the substrate backside (i.e., the particles exposed on the substrate surface side) become smaller in cross section near the substrate backside. As a result, a sufficient current path can not be obtained, which may cause a decrease in luminous efficiency, but the details are not clear.

However, since the crystallinity of the interface between the columnar structures constituting the gallium nitride self-supporting substrate is lowered, when used as the light emitting functional layer of the light emitting device, the light emitting efficiency is lowered, the light emitting wavelength is varied, . Therefore, the larger the cross-sectional average diameter of the columnar structure is, the better. Preferably, the cross-sectional mean diameter of the semiconductor single crystal grain on the outermost surface of the gallium nitride self-supporting substrate is 0.3 占 퐉 or more, more preferably 3 占 퐉 or more, further preferably 20 占 퐉 or more, particularly preferably 50 占 퐉 or more , And most preferably 70 mu m or more. The upper limit of the cross-sectional average diameter of the semiconductor monocrystalline grains on the outermost surface of the gallium nitride self-supporting substrate is not particularly limited. However, the upper limit is not more than 1000 mu m, more practically, not more than 500 mu m, and more practically, not more than 200 mu m. In order to produce semiconductor single-crystal grains having such a cross-sectional average diameter, it is preferable that the sintered grain size on the surface of the grain constituting the oriented polycrystalline sintered body used for producing the gallium nitride self-supporting substrate is 0.3 to 1000 탆 More preferably 3 탆 to 1000 탆, further preferably 10 탆 to 200 탆, and particularly preferably 14 탆 to 200 탆. Alternatively, in the case where the cross-sectional average diameter of the semiconductor single crystal particles on the outermost surface of the gallium nitride self-supporting substrate is made larger than the average cross-sectional average diameter of the back surface of the self-supporting substrate, It is preferable that the sintered grain size is from 10 mu m to 100 mu m, and more preferably from 14 mu m to 70 mu m.

The gallium nitride single crystal particles constituting the gallium nitride self-supporting substrate may not contain a dopant. Here, the expression " does not include a dopant " means that it does not contain an element added for the purpose of imparting any function or characteristic, and it is needless to say that the inevitable impurity content is allowed. Alternatively, the gallium nitride single crystal particles constituting the gallium nitride self-supporting substrate may be doped with an n-type dopant or a p-type dopant. In this case, the gallium nitride self-supporting substrate may be a p-type electrode, an n-type electrode, a p- It can be used as a member or a layer other than a substrate such as a mold layer. Preferable examples of the p-type dopant include at least one selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), zinc (Zn) and cadmium (Cd). Preferable examples of the n-type dopant include at least one selected from the group consisting of silicon (Si), germanium (Ge), tin (Sn), and oxygen (O).

The gallium nitride single crystal particles constituting the gallium nitride self-supporting substrate may be mixed to control the bandgap. Preferably, the gallium nitride single crystal particles may be composed of gallium nitride which is hornblended with at least one crystal selected from the group consisting of AlN and InN, and the p-type gallium nitride and / or n-type gallium nitride single crystal particles may be The p-type dopant or the n-type dopant may be doped in the gallium nitride which is purified. For example, Mg can be doped into Al _x Ga _{1 - x} N, which is a mixed crystal of gallium nitride and AlN, to be used as an n-type substrate by doping Si on p-type substrate and Al _x Ga _{1 - x} N. When the self-supporting substrate is used as the light-emitting functional layer of the light-emitting element, the band gap is widened by mixing the gallium nitride with AlN, and the light emission wavelength can be shifted toward the high energy. Further, the gallium nitride may be a mixed crystal with InN, thereby narrowing the bandgap and shifting the emission wavelength toward the low energy.

The gallium nitride self-standing substrate preferably has a size of at least 2 inches in diameter, more preferably at least 4 inches in diameter, and more preferably at least 8 inches in diameter. As the number of gallium nitride self-supporting substrates increases, the number of devices that can be fabricated increases, which is preferable from the viewpoint of manufacturing cost, and the degree of freedom of the device area increases from the viewpoint of the area light emitting device. And the upper limit of the area or size is not necessarily defined. On the other hand, the gallium nitride self-supporting substrate is preferably circular or substantially circular when viewed from the top, but is not limited thereto. When it is not a circular shape or a substantially circular shape, the area is preferably 2026 mm ² or more, more preferably 7850 mm ² or more, further preferably 31400 mm ² or more. However, for applications not requiring a large area, it may be an area smaller than the above range, for example, a diameter of 50.8 mm (2 inches) or less and an area conversion of 2026 mm ² or less. The thickness of the gallium nitride self-supporting substrate needs to be able to impart independence to the substrate, and is preferably 20 占 퐉 or more, more preferably 100 占 퐉 or more, and still more preferably 300 占 퐉 or more. The upper limit of the thickness of the gallium nitride self-supporting substrate is not necessarily defined, but from the viewpoint of the manufacturing cost, it is realistic to be 3000 占 퐉 or less.

The aspect ratio (T / D _T ) defined as the ratio of the thickness T of the gallium nitride self-supporting substrate to the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride self- Is preferably 0.7 or more, more preferably 1.0 or more, and further preferably 3.0 or more. This aspect ratio is preferable from the viewpoint of increasing the luminous efficiency in the case of using an LED. It is considered that the reason why the luminous efficiency is increased is that the defect density of gallium nitride in the high aspect ratio non-particle side is low and the extraction efficiency of light is increased, but the details are not clear.

(1) The light-emitting functional layer is preferably fabricated on the side of the surface of the self-supporting substrate (on the side opposite to the side in contact with the oriented polycrystalline sintered body as the base substrate at the time of manufacturing), and (2) (D _T / D _B ) of the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the back surface of the self-supporting substrate is preferably an appropriate value, and (3) (4) the aspect ratio (T / D _T ) of the particles constituting the self-supporting substrate is preferably as large as possible. From the viewpoints of (3) and (4), it is preferable that the cross-section average diameter is large and the aspect ratio is large, in other words, the gallium nitride crystal having a large cross-section average diameter on the substrate front surface side is preferable. From the standpoint of self-assembly, the thickness of the gallium nitride self-supporting substrate is preferably 20 占 퐉 or more, more preferably 100 占 퐉 or more, and still more preferably 300 占 퐉 or more. However, as described above, if the thickness of the gallium nitride crystal is increased, it is not preferable from the viewpoint of cost. That is, the thickness of the gallium nitride self-supporting substrate is not more than 3000 mu m, preferably not more than 600 mu m, and preferably not more than 300 mu m. Therefore, the thickness of 50 to 500 mu m is preferable, and the thickness of 50 to 300 mu m is more preferable, in terms of both the point of raising the light emission efficiency while self-supporting and the cost point of view.

Manufacturing method

(1) preparing an oriented polycrystalline sintered body; (2) forming a seed crystal layer composed of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body; (3) forming a layer made of gallium nitride crystal having a thickness of 20 탆 or more on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer, (4) removing the oriented polycrystalline sintered body , Thereby obtaining a gallium nitride self-supporting substrate.

(1) oriented polycrystalline sintered body

An oriented polycrystalline sintered body is prepared as a ground substrate for manufacturing a gallium nitride self-supporting substrate. The composition of the oriented polycrystalline sintered body is not particularly limited, but it is preferably one selected from the oriented polycrystalline alumina sintered body, the oriented polycrystalline zinc oxide sintered body and the oriented polycrystalline aluminum nitride sintered body. Since the oriented polycrystalline sintered body can be efficiently produced through molding and firing using a commercially available plate-like powder, it can be manufactured at low cost, and is easy to be molded, and is therefore suitable for large-size production. According to the knowledge of the present inventors, it is possible to manufacture a gallium nitride self-standing substrate suitable for manufacturing a large-area light emitting device at a low cost by using an oriented polycrystalline sintered body as a base substrate and growing a plurality of semiconductor single crystal grains thereon have. As a result, the gallium nitride self-supporting substrate is very suitable for manufacturing a large-area light emitting device at low cost.

The oriented polycrystalline sintered body is composed of a sintered body including a plurality of single crystal grains, and a plurality of single crystal grains are oriented to a certain degree or to a high degree in a certain direction. By using the oriented polycrystalline sintered body, it is possible to manufacture a gallium nitride self-supporting substrate having a substantially aligned crystal orientation in a substantially normal direction, and a gallium nitride based material is epitaxially grown on the gallium nitride self- A state in which the crystal orientation is substantially aligned in the normal direction is realized. Therefore, when such a gallium nitride self-standing substrate having high orientation is used as a substrate for a light-emitting device, the light-emitting functional layer can likewise be formed in a state in which the crystal orientation is substantially aligned in a substantially normal direction, High luminous efficiency can be realized. Alternatively, even when the gallium nitride self-standing substrate having a high orientation property is used as the light emitting functional layer of the light emitting device, high luminous efficiency equivalent to that in the case of using a single crystal substrate can be realized. Regardless, in order to manufacture a gallium nitride self-supporting substrate having such a high orientation, it is necessary to use the oriented polycrystalline sintered body as a base substrate. It is preferable that the oriented polycrystalline sintered body has transparency, but this is not limitative. In the case of having transparency, a technique such as laser lift-off may be used when removing the oriented polycrystalline plate. Examples of the method for producing the oriented polycrystalline sintered body include a hot isostatic pressing method (HIP), a hot pressing method (HP), a discharge plasma sintering method (HIP), and a sintering method in addition to a normal atmospheric pressure sintering method using an atmospheric furnace, (SPS), or a combination of these methods.

The oriented polycrystalline sintered body preferably has a size of at least 2 inches in diameter, more preferably at least 4 inches in diameter, and more preferably at least 200 inches in diameter. The larger the orientation polycrystalline sintered body is, the larger the area of the gallium nitride self-supporting substrate that can be fabricated increases, and accordingly, the number of the light emitting elements that can be manufactured increases, which is preferable from the viewpoint of manufacturing cost. In addition, from the viewpoint of a surface light emitting device, the degree of freedom of the device area is increased, and it is preferable from the viewpoint of widening the application to the surface emitting illumination, etc., and the upper limit is not necessarily defined in the area or the size. On the other hand, the gallium nitride self-supporting substrate is preferably circular or substantially circular when viewed from the top, but is not limited thereto. When it is not circular or substantially circular, it preferably has an area of 2026 mm ² or more, more preferably 7850 mm ² or more, and still more preferably 31400 mm ² or more. However, for applications not requiring a large area, it may be an area smaller than the above range, for example, a diameter of 50.8 mm (2 inches) or less and an area conversion of 2026 mm ² or less. The thickness of the oriented polycrystalline sintered body is not particularly limited as long as it is self-supporting, but it is not preferable from the viewpoint of manufacturing cost if it is excessively thick. Therefore, it is preferably 20 占 퐉 or more, more preferably 100 占 퐉 or more, and further preferably 100 to 1000 占 퐉. On the other hand, when the gallium nitride film is formed, the stress caused by the difference in thermal expansion between the alumina and the gallium nitride may warp the entire substrate, which may interfere with the subsequent process. The stress varies depending on the film-forming method of the gallium nitride, the film forming conditions, the material of the oriented polycrystalline sintered body, the film thickness, the substrate diameter, etc. However, as one of the methods for suppressing the warp caused by the stress, even if a thick oriented polycrystalline sintered body is used good. The thickness of the oriented polycrystalline alumina sintered body may be 900 占 퐉 or more when fabricating a gallium nitride self-supporting substrate having a diameter of 50.8 mm (2 inches) and a thickness of 300 占 퐉 by using the oriented polycrystalline alumina sintered body as the underlying polycrystalline sintered body, And may be 1300 占 퐉 or more or 2000 占 퐉 or more. In this way, the thickness of the oriented polycrystalline sintered body can be suitably selected in consideration of the viewpoint of the production cost and the viewpoint of suppression of warping.

The average particle diameter of the particles constituting the oriented polycrystalline sintered body is preferably 0.3 to 1000 占 퐉, more preferably 3 to 1000 占 퐉, still more preferably 10 to 200 占 퐉, particularly preferably 14 占 퐉 To 200 mu m. Alternatively, as described above, when considering that the cross-sectional average diameter of the semiconductor single crystal grain on the outermost surface of the gallium nitride self-supporting substrate is made larger than the cross-sectional average diameter of the back surface of the self-supporting substrate, It is preferable that the sintered grain size on the surface of the plate be 10 mu m to 100 mu m, more preferably 14 mu m to 70 mu m. The average particle diameter of the oriented polycrystalline sintered body as a whole is in correlation with the average particle diameter of the surface of the substrate. If the average particle diameter is within these ranges, the mechanical strength of the sintered body is excellent and handling is easy. In addition, when a light emitting device is fabricated by forming a light emitting functional layer on the top and / or inside of the gallium nitride self-supporting substrate manufactured using the oriented polycrystalline sintered body, the light emitting function layer is also excellent in light emission efficiency. On the other hand, the average particle diameter of the sintered body particles on the surface of the sintered body in the present invention is measured by the following method. That is, the plate surface of the plate-shaped sintered body is polished and an image is taken by a scanning electron microscope. The visual range is a visual range in which a line intersecting any straight line or 10 to 30 particles is drawn when a straight line is drawn on the diagonal line of the obtained image. A straight line of two lines is drawn on the diagonal line of the obtained image and a value obtained by multiplying the average of the lengths of the inner line segments of the individual particles by 1.5 with respect to all the particles whose straight lines intersect is taken as the average particle diameter of the plate surface. On the other hand, when the interface of the sintered product particles can not be clearly identified by the image of the scanning microscope on the printing plate surface, the treatment for making the interface stand out by thermal etching (for example, at 1550 캜 for 45 minutes) or chemical etching The above evaluation may be performed.

A particularly preferred oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body. The alumina is aluminum oxide (Al ₂ O ₃ ), typically α-alumina having the same corundum structure as single crystal sapphire, and the oriented polycrystalline alumina sintered body is obtained by sintering in the state in which a large number of alumina crystal grains are oriented It is a solid formed by mutual bonding. The alumina crystal grains are particles composed of alumina and may contain other elements such as dopants and unavoidable impurities, or alumina and inevitable impurities. The oriented polycrystalline alumina sintered body may contain an additive as a sintering aid as a grain boundary phase. In addition, the oriented polycrystalline alumina sintered body may contain other phases other than the alumina crystal grains or other elements as described above, but is preferably composed of alumina crystal grains and unavoidable impurities. The oriented surface of the oriented polycrystalline alumina sintered body is not particularly limited and may be c-plane, a-plane, r-plane or m-plane.

The orientation crystal orientation of the oriented polycrystalline alumina sintered body is not particularly limited and may be c-plane, a-plane, r-plane or m-plane or the like and is preferably oriented in the c-plane from the viewpoint of lattice constant matching with the gallium nitride self- . Regarding the degree of orientation, for example, the degree of orientation on the plate surface is preferably 50% or more, more preferably 65% or more, still more preferably 75% or more, particularly preferably 85% 90% or more, and most preferably 95% or more. The degree of orientation is measured by measuring the XRD profile when X-ray is irradiated on the plate surface of the plate-shaped alumina using an XRD apparatus (for example, RINT-TTR III manufactured by Rigaku Corporation) .

On the other hand, the crystallinity of constituent particles of the gallium nitride self-supporting substrate tends to be high, and the density of defects such as dislocations can be suppressed to a low level. Therefore, it is considered that the gallium nitride self-standing substrate can be used preferably in comparison with the gallium nitride single crystal substrate in any kind of application such as a light emitting device. For example, when a functional layer is fabricated on a gallium nitride self-supporting substrate by epitaxial growth, the functional layer grows generally on the underlying gallium nitride self-supporting substrate to become an aggregate of columnar structures. In epitaxial growth, since the crystal quality of the base is inherited, a high crystal quality can be obtained in each domain unit of the columnar structure constituting the functional layer. The reason why the defect density of the crystal grains constituting the gallium nitride self-sustaining substrate is low is not clear. However, among the lattice defects generated at the initial stage of fabrication of the gallium nitride self-sustaining substrate, the growth in the horizontal direction is absorbed by the grain boundaries and disappears I guess.

From the viewpoint of decreasing the density of defects such as dislocation contained in the gallium nitride self-supporting substrate, in the case of manufacturing the gallium nitride self-supporting substrate, a part or all of the particles constituting the outermost surface of the oriented polycrystalline sintered body, (For example, a reference orientation such as a c-plane, a-plane, or the like). The inclined paper may be inclined at substantially all or some of the inclined paper at a substantially constant angle, or may be inclined at various angles and / or in various directions having a distribution within a certain range (preferably 0.01 to 20). In addition, the sloped particle and the non-inclined particle may be mixed at a desired ratio. Alternatively, the plate surface of the oriented polycrystalline alumina sintered body may be obliquely polished with respect to the reference plane, and the exposed surface of the particles may be inclined in a certain direction. Alternatively, a slightly inclined surface in the reference orientation of the outermost surface particles may be exposed It may be. In any of the above cases, the alumina single crystal particles constituting the outermost surface of the oriented polycrystalline alumina sintered body oriented in the reference orientation such as the c-plane, the a-plane and the like have a part or all of their reference orientations of 0.5 to 20 It is preferable to be inclined to be turned within the range.

The oriented polycrystalline alumina sintered body can be produced by forming and sintering using a plate-shaped alumina powder as a raw material. The flaked alumina powder is commercially available and is commercially available. The type and shape of the flaky alumina powder are not particularly limited as long as a dense oriented polycrystalline alumina sintered body can be obtained. However, the average particle diameter may be 0.4 to 15 mu m and the thickness may be 0.05 to 1 mu m, May be mixed with two or more kinds. Preferably, the sheet-like alumina powder is oriented by a technique using a shear force to obtain an oriented molded article. Preferable examples of the method using the shear force include tape forming, extrusion molding, doctor blade method, and any combination thereof. In any of the above-described methods, an orientation method using a shearing force is preferably carried out by appropriately adding additives such as a binder, a plasticizer, a dispersant, and a dispersion medium to a slurry of the flaky alumina powder, passing the slurry through fine slit- In the form of a sheet. The slit width of the discharge port is preferably 10 to 400 mu m. On the other hand, the amount of the dispersion medium is preferably such an amount that the slurry viscosity is 5000 to 100000 cP, more preferably 20,000 to 60,000 cP. The thickness of the oriented molded article formed into a sheet shape is preferably 5 to 500 占 퐉, more preferably 10 to 200 占 퐉. It is preferable that a plurality of the oriented molded articles molded in the sheet form are superimposed to form a precursor laminate having a desired thickness and press molding is performed on the precursor laminate. This press molding can be preferably carried out by an isostatic pressing at a pressure of 10 to 2000 kgf / cm < 2 > in warm water at 50 to 95 DEG C by packing the precursor laminate in a vacuum pack or the like. Further, the oriented molded article obtained by molding in the form of a sheet or the precursor laminate may be subjected to a treatment by a roll press method (for example, a heating roll press or a calender roll). Further, in the case of using extrusion molding, it is also possible to pass the fine discharge port in the mold by the design of the flow path in the mold, and then the sheet-like molded body may be integrated in the mold so that the molded body is discharged in a laminated state. It is preferable to degrease the obtained molded article according to known conditions. The orientation-molded product obtained as described above is subjected to ordinary atmospheric pressure sintering using air or the like in a nitrogen atmosphere or a hydrogen atmosphere and is then subjected to hot isostatic pressing (HIP), hot pressing (HP), discharge plasma sintering (SPS ), And a combination thereof to form an alumina sintered body comprising the alumina crystal grains oriented. The firing temperature and firing time in the firing are varied depending on the firing method, but the firing temperature is 1000 to 1950 ° C, preferably 1100 to 1900 ° C, more preferably 1500 to 1800 ° C, firing time is 1 minute to 10 hours, Preferably 30 minutes to 5 hours. The first sintering step in which the sintered body is sintered at a temperature of 1500 to 1800 ° C for 2 to 5 hours and a surface pressure of 100 to 200 kgf / cm 2, and a sintered body obtained by hot isostatic pressing (HIP) More preferably at a temperature of -1800 占 폚 for 30 minutes to 5 hours, and at a gas pressure of 1000 to 2000 kgf / cm2. The firing time at the firing temperature is not particularly limited, but is preferably 1 to 10 hours, and more preferably 2 to 5 hours. When light transmittance is imparted, a method of firing the sheet-like alumina powder of high purity as a raw material at 1100 to 1800 ° C for 1 minute to 10 hours in the atmosphere, hydrogen atmosphere, nitrogen atmosphere or the like is preferably exemplified . The obtained sintered body may be sintered again by hot isostatic pressing (HIP) at 1200 to 1400 占 폚 or at 1400 to 1950 占 폚 for 30 minutes to 5 hours under a gas pressure of 300 to 2000 kgf / cm2. Since the grain boundary phase is preferably small, the plate-like alumina powder is preferably high purity, more preferably 98% or more in purity, more preferably 99% or more, particularly preferably 99.9% or more, most preferably, 99.99% or more. On the other hand, the firing conditions are not limited to those described above. For example, the second firing step by hot isostatic pressing (HIP) may be omitted if densification and high orientation can be achieved at the same time. In addition, a very small amount of additives may be added to the raw material as a sintering auxiliary agent. The addition of the sintering aid is intended to reduce the pore size, which is one of the scattering factors of the light, and consequently to improve the light transmittance, though the weight loss of the grain boundary phase is reversed. As such a sintering _{aid, MgO, ZrO 2, Y 2} O 3, CaO, SiO 2, TiO 2, Fe 2 O 3, Mn 2 O 3, La 2 O 3 , such as the _{oxide, AlF 3, MgF 2, YbF} 3 , etc. And the like, and the like. Of these, MgO, CaO, SiO ₂ and La ₂ O ₃ are preferable, and MgO is particularly preferable. However, from the viewpoint of light transmittance, the amount of the additive should be suppressed to a necessary minimum, preferably not more than 5000 ppm, more preferably not more than 1000 ppm, further preferably not more than 700 ppm.

The oriented polycrystalline alumina sintered body can also be produced by molding and sintering using mixed powder obtained by appropriately adding flaky alumina powder to fine alumina powder and / or transition alumina powder as a raw material. In this production method, a so-called TGG (Templated Grain Growth) process in which the flaky alumina powder becomes a seed crystal (template) and the fine alumina powder and / or transition alumina powder become a matrix and the template receives the matrix and is homoepitaxially grown As a result, crystal growth and densification occur. The particle size of the flaky alumina particles and the matrix to be used as the template is liable to cause grain growth if the particle size ratio is large. For example, when the average particle size of the template is 0.5 to 15 μm, the average particle size of the matrix is preferably 0.4 μm or less, Is not more than 0.2 mu m, and more preferably not more than 0.1 mu m. For example, when a template alumina powder having an average particle size of 2 mu m and a fine alumina powder having an average particle size of 0.1 mu m are used as the matrix, the ratio of the template / matrix to the template / matrix ratio is 50 / 50 to 1/99 wt%. Further, as a sintering aid in the viewpoint of progress _{densification, MgO, ZrO 2, Y 2} O 3, CaO, SiO 2, TiO 2, Fe 2 O 3, Mn 2 O 3, La 2 O 3 oxide, such as, AlF ₃ , Fluoride such as MgF ₂ , YbF ₃ and the like may be added, and MgO, CaO, SiO ₂ and La ₂ O ₃ are preferable, and MgO is particularly preferable. In such a method, in addition to the normal atmospheric pressure sintering using the atmosphere, the nitrogen atmosphere and the hydrogen atmosphere described above, pressurization such as hot isostatic pressing (HIP), hot pressing (HP), discharge plasma sintering (SPS) Sintered body, and a combination thereof, a high quality oriented polycrystalline alumina sintered body can be obtained.

The alumina sintered body thus obtained is a polycrystalline alumina sintered body oriented in a desired plane such as a c-plane depending on the kind of the plate-like alumina powder serving as the raw material described above. The oriented polycrystalline alumina sintered body thus obtained is ground to a planar surface by grinding it with a grinding stone, and then the plate surface is smoothed by lapping using diamond abrasive grains to obtain an oriented alumina substrate.

(2) Formation of seed crystal layer

A seed crystal layer made of gallium nitride is formed on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body. On the other hand, " to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body " means a structure brought about by crystal growth influenced by the crystal orientation of the oriented polycrystalline sintered body, The structure is not limited to the grown structure but includes a structure in which the crystal grows in a crystal orientation different from that of the oriented polycrystalline sintered body. The method for producing the seed crystal layer is not particularly limited, but a vapor phase method such as MOCVD (metal organic vapor phase epitaxy), MBE (molecular beam epitaxy), HVPE (halide vapor phase epitaxy), or sputtering, Na flux method, A hydrothermal method such as a hydrothermal method and a sol-gel method, a powder method using solid phase growth of a powder, and a combination thereof. For example, the formation of the seed crystal layer by the MOCVD method is preferably performed by depositing a low-temperature GaN layer at 450 to 550 캜 at 20 to 50 nm and then laminating a GaN film having a thickness of 2 to 4 탆 at 1000 to 1200 캜 .

(3) Formation of a gallium nitride crystal layer

A layer made of a gallium nitride crystal having a thickness of 20 占 퐉 or more is formed on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer. The method of forming the layer composed of the gallium nitride crystal is not particularly limited as long as it has a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body and / or the seed crystal layer, and may be formed by vapor phase method such as MOCVD, HVPE, Na flux method, A liquid method such as a thermal method, a hydrothermal method and a sol-gel method, a powder method using solid phase growth of a powder, and a combination thereof are preferable, but it is particularly preferable to use a Na flux method. According to the Na flux method, a thick gallium nitride crystal layer with high crystallinity can be efficiently fabricated on the seed crystal layer. The formation of the gallium nitride crystal layer by the Na flux method can be carried out by adding a metal Ga, a metal Na and, if desired, dopants (such as germanium (Ge), silicon (Si) A dopant or a p-type dopant such as beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), zinc (Zn), cadmium (Cd), etc.) It is preferable to increase the temperature to 830 to 910 ° C and to 3.5 to 4.5 MPa, and then rotate while maintaining the temperature and the pressure. The holding time is different depending on the desired film thickness, but it may be about 10 to 100 hours. Further, it is preferable that the gallium nitride crystal obtained by the Na flux method is ground with a grinding stone so as to flatten the plate surface, and then the plate surface is smoothed by lapping using diamond abrasive grains.

(4) Removal of oriented polycrystalline sintered body

The oriented polycrystalline sintered body is removed to obtain a gallium nitride self-supporting substrate. The method of removing the oriented polycrystalline sintered body is not particularly limited, and examples thereof include grinding, chemical etching, interfacial heating (laser lift off) by laser irradiation from the oriented sintered body side, spontaneous exfoliation using the difference in thermal expansion at the time of heating .

Light emitting device and method of manufacturing

A high-quality light emitting device can be manufactured using the above-described gallium nitride self-supporting substrate according to the present invention. The structure of the light emitting device using the gallium nitride self-supporting substrate of the present invention and the manufacturing method thereof are not particularly limited. Typically, the light-emitting element is fabricated by providing a light-emitting functional layer on a gallium nitride self-supporting substrate, and the light-emitting functional layer is formed by a single crystal structure in a substantially normal direction so as to have a crystal orientation substantially corresponding to the crystal orientation of the gallium nitride substrate It is preferable to fabricate at least one layer composed of a plurality of semiconductor single crystal particles having a predetermined thickness. However, the gallium nitride self-supporting substrate may be used as a member or layer other than a substrate such as an electrode (which may be a p-type electrode or an n-type electrode), a p-type layer or an n-type layer. The element size is not particularly limited, and may be a small element of 5 mm x 5 mm or less, or a surface light emitting element of 10 cm x 10 cm or more.

FIG. 1 schematically shows a layer structure of a light emitting device according to an embodiment of the present invention. 1 includes a gallium nitride self-sustaining substrate 12 and a light-emitting functional layer 14 formed on the substrate. The light-emitting functional layer 14 is provided with at least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a direction of a normal line. The light-emitting functional layer 14 emits light based on the principle of a light-emitting element such as an LED by applying an appropriate voltage to an electrode or the like. In particular, by using the gallium nitride self-standing substrate 12 of the present invention, it is expected to obtain a light emitting device having the same light emitting efficiency as that in the case of using a gallium nitride single crystal substrate, thereby realizing a remarkably low cost. Further, by using gallium nitride which is made conductive by the introduction of the p-type or n-type dopant as the substrate, it is possible to realize a vertical-structured light-emitting device, thereby increasing the luminance. In addition, a large area light emitting element can be realized at low cost.

A light-emitting functional layer 14 is formed on the substrate 12. The light-emitting functional layer 14 may be provided on the entire surface or part of the substrate 12 and may be provided on the entire surface or part of the buffer layer when a buffer layer described later is formed on the substrate 12. [ The light-emitting functional layer 14 is provided with at least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a direction of a normal line. When the electrode and / or the fluorescent material are appropriately installed and a voltage is applied, Various known layer arrangements for emitting light based on the principle of the light emitting element to be used can be employed. Therefore, the light-emitting functional layer 14 may emit visible light such as blue or red, or may emit ultraviolet light with or without visible light. The light emitting function layer 14 preferably constitutes at least a part of the light emitting device using the pn junction. This pn junction is formed between the p-type layer 14a and the n-type layer 14c And may include the active layer 14b. At this time, double heterojunction or single heterojunction (hereinafter, referred to as heterojunction) using a layer having a smaller bandgap than the p-type layer and / or the n-type layer may be used as the active layer. As a form of the p-type layer-active layer-n-type layer, a quantum well structure in which the thickness of the active layer is reduced can be adopted. Needless to say, in order to obtain a quantum well, a double hetero-junction in which the band gap of the active layer is smaller than that of the p-type layer and the n-type layer must be adopted. Further, a multiple quantum well structure (MQW) in which a plurality of these quantum well structures are stacked may be used. By taking these structures, the luminous efficiency can be enhanced as compared with the p-n junction. As described above, the light-emitting functional layer 14 preferably has a p-n junction and / or a hetero junction and / or a quantum well junction having a light emitting function.

Therefore, the at least one layer constituting the light-emitting functional layer 14 is at least one selected from the group consisting of an n-type layer doped with an n-type dopant, a p-type layer doped with a p-type dopant and an active layer . The n-type layer, the p-type layer, and the active layer (if present) may be made of the same material as the main component, or may be made of a material whose main component is different from each other.

The material of each layer constituting the light-emitting functional layer 14 is not particularly limited as long as it has a crystal orientation of the gallium nitride self-supporting substrate generally grown and has a light emitting function. However, a material such as a gallium nitride (GaN) ) -Based material and an aluminum nitride (AlN) -based material, and may suitably contain a dopant for controlling the p-type to the n-type. A particularly preferable material is a gallium nitride (GaN) -based material which is the same kind of material as the gallium nitride self-supporting substrate. In addition, the material constituting the light-emitting functional layer 14 may be a mixed crystal obtained by solid-solving AlN, InN or the like in GaN, for example, in order to control the band gap. Further, as described in the immediately preceding paragraph, the light emitting functional layer 14 may be a heterojunction formed of a plurality of material systems. For example, a gallium nitride (GaN) -based material may be used for the p-type layer and a zinc oxide (ZnO) -based material may be used for the n-type layer. Further, a zinc oxide (ZnO) based material may be used for the p-type layer, and a gallium nitride (GaN) based material may be used for the active layer and the n-type layer.

Each layer constituting the light-emitting functional layer 14 is composed of a plurality of semiconductor single crystal particles having a single crystal structure in a substantially normal direction. That is, each layer is composed of a plurality of semiconductor single crystal grains two-dimensionally connected in a horizontal plane direction, and therefore, has a single crystal structure in a substantially normal direction. Therefore, each layer of the light-emitting functional layer 14 is not a single crystal as a whole but has a single crystal structure in a local domain unit, and thus can have a crystallinity sufficiently high to ensure a luminescent function. Preferably, the semiconductor single crystal particles constituting each layer of the light-emitting functional layer 14 have a structure in which the crystal orientation of the gallium nitride self-supporting substrate as the substrate 12 is substantially grown. Refers to a structure in which crystal growth is effected by a crystal orientation of a gallium nitride self-supporting substrate, and a structure in which the crystal orientation of a gallium nitride self-supporting substrate is completely grown And the crystal orientation of the gallium nitride self-supporting substrate may be grown to some extent as long as the desired light emitting function can be ensured. That is, this structure also includes a structure that grows in a crystal orientation different from that of the oriented polycrystalline sintered body. In this sense, the expression " a structure grown substantially along the crystal orientation " may be referred to as a " structure grown largely from a crystal orientation. &Quot; Such crystal growth is preferably performed by epitaxial growth, but the present invention is not limited to this, and various crystal growth types similar thereto may be used. In particular, when each of the layers constituting the n-type layer, the active layer and the p-type layer grows in the same crystal orientation as the gallium nitride self-supporting substrate, the crystal orientation between the gallium nitride self- And a good luminescence characteristic can be obtained. That is, when the light emitting function layer 14 also grows substantially along the crystal orientation of the gallium nitride self-supporting substrate 12, the orientation becomes substantially constant in the vertical direction of the substrate. Therefore, in the case of using the gallium nitride self-supporting substrate to which the n-type dopant is added, the normal direction is the same as that of the single crystal. In the case of using the gallium nitride self-supporting substrate as the cathode, When the gallium nitride self-supporting substrate is used, the light emitting device having a vertical structure in which the gallium nitride self-supporting substrate is an anode can be obtained.

At least the respective layers of the n-type layer, the active layer and the p-type layer constituting the light-emitting function layer 14 are grown in the same crystal orientation, each layer of the light-emitting functional layer 14 is formed of single crystal It is also possible to grasp that it is an aggregate of semiconductor single crystal particles of the columnar structure in which the grain boundary is observed when viewed from the cut plane in the horizontal plane direction. Here, the " columnar structure " does not only mean a typical vertically long columnar shape but also a meaning including various shapes such as a horizontally elongated shape, a trapezoidal shape, and a trapezoidal inverted shape. However, as described above, each layer is a structure in which the crystal orientation of the gallium nitride self-supporting substrate is grown to some extent, and it does not necessarily have to be a columnar structure in a strict sense. It is considered that the cause of the columnar structure is that the semiconductor single crystal grain grows under the influence of the crystal orientation of the gallium nitride self-supporting substrate which is the substrate 12 as described above. For this reason, it is considered that the average grain size (hereinafter referred to as the section average diameter) of the cross section of the semiconductor single crystal grain, which is also referred to as the columnar structure, depends not only on the film forming conditions but also on the average grain size of the gallium nitride self- The interface of the columnar structure constituting the light-emitting functional layer affects the luminous efficiency and the emission wavelength. The presence of the grain boundaries results in a poor light transmittance in the cross-sectional direction, and the light is scattered or reflected. Therefore, in the case of a structure for extracting light in the normal direction, the effect of increasing the luminance by the scattered light from the grain boundaries is also expected.

However, since the crystallinity of the interface between the columnar structures constituting the light-emitting functional layer 14 is lowered, there is a possibility that the luminous efficiency is lowered, the emission wavelength is varied, and the emission wavelength is widened. Therefore, the larger the cross-sectional average diameter of the columnar structure is, the better. Preferably, the cross-sectional mean diameter of the semiconductor single crystal grain on the outermost surface of the light-emitting functional layer 14 is 0.3 占 퐉 or more, more preferably 3 占 퐉 or more, further preferably 20 占 퐉 or more, 50 mu m or more, and most preferably 70 mu m or more. The upper limit of the cross-sectional average diameter is not particularly limited, but is not more than 1000 占 퐉, more realistic, not more than 500 占 퐉, and more practically not more than 200 占 퐉. In order to manufacture semiconductor single-crystal particles having such a cross-sectional average diameter, it is preferable that the cross-sectional average diameter of the outermost surface of the substrate of gallium nitride monocrystalline grains constituting the gallium nitride self-supporting substrate is 0.3 to 1000 탆 , And more preferably 3 m or more.

When a material other than a gallium nitride (GaN) based material is used for part or all of the light-emitting function layer 14, a buffer layer for suppressing the reaction is provided between the gallium nitride self-standing substrate 12 and the light- . The main component of such a buffer layer is not particularly limited, but it is preferably composed of a material containing as a main component at least one selected from a zinc oxide (ZnO) -based material and an aluminum nitride (AlN) -based material, But may appropriately include a dopant for control.

It is preferable that each layer constituting the light-emitting functional layer 14 is made of a gallium nitride-based material. For example, an n-type gallium nitride layer and a p-type gallium nitride layer may be successively grown on the gallium nitride self-supporting substrate 12, and the order of stacking the p-type gallium nitride layer and the n-type gallium nitride layer may be reversed. Preferable examples of the p-type dopant used for the p-type gallium nitride layer are selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), zinc (Zn) and cadmium One or more species can be mentioned. Preferable examples of the n-type dopant used for the n-type gallium nitride layer include at least one selected from the group consisting of silicon (Si), germanium (Ge), tin (Sn) and oxygen (O). The p-type gallium nitride layer and / or the n-type gallium nitride layer may be composed of gallium nitride mixed with at least one crystal selected from the group consisting of AlN and InN, and the p-type layer and / or n- The impurity-doped gallium nitride may be doped with a p-type dopant or an n-type dopant. For example, p-type layer, Al _x Ga ₁ by doping Mg on the mixed crystal of Al _x Ga _{1 -x} N of GaN and AlN _- by doping with Si to N _x can be used as the n-type layer. By mixing gallium nitride with AlN, the bandgap is widened and the emission wavelength can be shifted toward higher energy. Further, the gallium nitride may be a mixed crystal with InN, thereby narrowing the bandgap and shifting the emission wavelength toward the low energy. at least one active layer made of GaN having a bandgap smaller than that of either layer or a mixed crystal of GaN and at least one selected from the group consisting of AlN and InN is provided between the p-type gallium nitride layer and the n-type gallium nitride layer It may be. The active layer has a structure in which the p-type layer and the n-type layer are double-hetero-junctioned. The thinned active layer corresponds to a light-emitting device having a quantum well structure, which is one mode of pn junction, and the luminous efficiency can be further increased. The active layer may have a band gap smaller than that of either one of the two layers and may be composed of a mixed crystal of GaN and at least one selected from the group consisting of GaN, AlN and InN. Even with such a single heterojunction, the luminous efficiency can be further increased. The gallium nitride buffer layer may be composed of undoped GaN or n-type or p-type doped GaN, and it may be made of AlN, InN or GaN having a lattice constant close to that of GaN, and at least one kind of crystal selected from the group consisting of AlN and InN And may be purified.

However, the light-emitting functional layer 14 may be composed of a plurality of material systems selected from a gallium nitride (GaN) based material, a zinc oxide based material, and an aluminum nitride (AlN) based material. For example, a p-type gallium nitride layer and an n-type zinc oxide layer may be grown on the gallium nitride self-supporting substrate 12, and the order of stacking the p-type gallium nitride layer and the n-type zinc oxide layer may be reversed. When the gallium nitride self-standing substrate 12 is used as a part of the light-emitting functional layer 14, an n-type or p-type zinc oxide layer may be formed. Preferable examples of the p-type dopant used for the p-type zinc oxide layer include nitrogen (N), phosphorus (P), arsenic (As), carbon (C), lithium (Li), sodium (Na) Silver (Ag), and copper (Cu). Preferred examples of the n-type dopant used for the n-type zinc oxide layer include aluminum (Al), gallium (Ga), indium (In), boron (B), fluorine (F), chlorine ), Iodine (I) and silicon (Si).

The method of forming the light-emitting functional layer 14 and the buffer layer is not particularly limited as long as the crystal orientation of the gallium nitride self-supporting substrate can be substantially grown, but a vapor phase method such as MOCVD, MBE, HVPE, or sputtering, a Na flux method, A hydrothermal method such as a hydrothermal method and a sol-gel method, a powder method using solid-phase growth of a powder, and a combination thereof are preferably exemplified. For example, in the case of fabricating the light emitting functional layer 14 made of a gallium nitride-based material by using the MOCVD method, a gas containing at least an organic metal gas (for example, trimethyl gallium) and nitrogen (N) (For example, ammonia) may be flown as a raw material on the substrate and grown in a temperature range of about 300 to 1200 DEG C in an atmosphere containing hydrogen, nitrogen, or both. In this case, an organic metal gas containing silicon (Si) and magnesium (Mg) (for example, trimethyl indium, trimethyl aluminum, monosilane , Disilane, bis-cyclopentadienyl magnesium) may be appropriately introduced to perform film formation.

When a material other than a gallium nitride-based material is used for the light-emitting functional layer 14 and the buffer layer, the seed crystal layer may be formed on the gallium nitride self-supporting substrate. The seed crystal layer is not limited to a film formation method or a material, but may be any one that promotes crystal growth that generally follows the crystal orientation. For example, when a zinc oxide-based material is used for part or all of the light-emitting functional layer 14, very thin zinc oxide seed crystals are produced by vapor phase growth methods such as MOCVD, MBE, HVPE, and sputtering It is also good.

The light emitting function layer 14 may further include an electrode layer 16 and / or a phosphor layer. As described above, since the light emitting device using the electrically conductive gallium nitride self-standing substrate 12 can employ a vertical structure, the electrode layer 18 is formed on the back surface of the gallium nitride self- However, the gallium nitride self-standing substrate 12 may be used as the electrode itself. In this case, it is preferable that the gallium nitride self-supporting substrate 12 is doped with an n-type dopant. When the electrode layer 16 on the light-emitting functional layer 14 is formed of a transparent conductive film such as ITO or a metal electrode having a high aperture ratio such as a lattice structure, The extraction efficiency of light generated in the functional layer 14 is increased.

When the luminescent functional layer 14 is capable of emitting ultraviolet light, a phosphor layer for converting ultraviolet light into visible light may be provided outside the electrode layer. The phosphor layer is not particularly limited as long as it is a layer containing a known fluorescent component capable of converting ultraviolet rays into visible light. For example, a fluorescent component that is excited by ultraviolet light to emit blue light, a fluorescent component that is excited by ultraviolet light to emit blue to green light, and a fluorescent component that is excited by ultraviolet light to emit red light are mixed, It is preferable to adopt a configuration in which white light is obtained. (Ca, Sr) ₅ (PO ₄ ) ₃ Cl: Eu, BaMgAl ₁₀ O ₁₇ : Eu, and Mn, Y ₂ O ₃ S: Eu are examples of preferable combinations of such fluorescent components. It is preferable to form the phosphor layer by dispersing in a resin such as silicone resin. Such a fluorescent component is not limited to the above exemplified material but may be a combination of other ultraviolet excited fluorescent material such as yttrium aluminum garnet (YAG), silicate fluorescent material, oxynitride fluorescent material, or the like.

On the other hand, when the luminescent functional layer 14 is capable of emitting blue light, a phosphor layer for converting blue light into yellow light may be provided outside the electrode layer. The phosphor layer is not particularly limited as long as it is a layer containing a known fluorescent component capable of converting blue light into yellow light. For example, it may be combined with a phosphor emitting yellow light such as YAG. By doing so, the blue light emitted from the phosphor layer and the yellow light emitted from the phosphor are in a complementary relationship, so that a pseudo-white light source can be obtained. On the other hand, the phosphor layer includes both a fluorescent component for converting blue light into yellow light and a fluorescent light component for converting ultraviolet light to visible light, so that both the conversion of ultraviolet light into visible light and the conversion of blue light into yellow light .

Usage

INDUSTRIAL APPLICABILITY The gallium nitride self-standing substrate of the present invention can be suitably used for various applications such as various electronic devices, power devices, light receiving devices, and solar cell wafers as well as the above-described light emitting devices.

Example

The present invention will be described more specifically with reference to the following examples.

Example 1

(1) Fabrication of c-plane oriented alumina sintered body

As a raw material, a flaky alumina powder (grade 00610, manufactured by Kinesei Tech Co., Ltd.) was prepared. 7 parts by weight of a binder (polyvinyl butyral: part number BM-2, manufactured by Sekisui Chemical Co., Ltd.), 10 parts by weight of a plasticizer (DOP: di (2-ethylhexyl) phthalate, Ltd.) and 2 parts by weight of a dispersant (Leodor SP-O30, manufactured by Kao Corporation) and a dispersion medium (2-ethylhexanol) were mixed. The amount of the dispersion medium was adjusted so that the slurry viscosity became 20000 cP. The slurry prepared as described above was formed into a sheet shape on a PET film by a doctor blade method so as to have a thickness after drying of 20 mu m. The obtained tape was cut into a circle of 50.8 mm (2 inches) in diameter, and then 150 sheets were stacked and placed on an Al plate having a thickness of 10 mm, and then vacuum packed. This vacuum pack was subjected to hydrostatic pressing at a pressure of 100 kgf / cm < 2 > in warm water at 85 DEG C to obtain a disk-shaped molded article.

The obtained molded article was placed in a degreasing furnace and degreased at 600 ° C for 10 hours. The obtained degreased body was fired in a hot press in nitrogen at 1600 占 폚 for 4 hours under a surface pressure of 200 kgf / cm2 using a graphite mold. The obtained sintered body was fired again in a hot isostatic pressing method (HIP) at 1700 占 폚 in argon for 2 hours under a gas pressure of 1500 kgf / cm2.

The thus-obtained sintered body was fixed to a base plate of a ceramics, and was ground to # 2000 using a grinder to flatten the plate surface. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 1 nm.

(2) Evaluation of oriented alumina substrate

(Evaluation of orientation degree)

In order to confirm the degree of orientation of the obtained aligned alumina substrate, the degree of orientation of the c-plane, which is the crystal face to be measured in this Experimental Example, was measured by XRD. An XRD profile was measured in the range of 2? = 20 to 70 占 when the plate surface of the oriented alumina substrate was irradiated with X-ray using an XRD apparatus (RINT-TTR III, manufactured by Rigaku Corporation). The c-plane orientation degree was calculated by the following equation. As a result, the value of the c-plane orientation degree in the present experimental example was 97%.

(Evaluation of particle diameter of sintered body particles)

Regarding the sintered body particles of the oriented alumina substrate, the average particle size of the plate surface was measured by the following method. The plate surface of the obtained aligned alumina substrate was polished and subjected to thermal etching at 1550 占 폚 for 45 minutes, and then an image was taken by a scanning electron microscope. The visual field range was set to a visual range in which a straight line intersecting a straight line or 10 to 30 particles was drawn when a straight line was drawn on the diagonal line of the obtained image. The average particle diameter of the surface of the sheet was defined as a value obtained by multiplying the average of the lengths of the inner line segments of the individual particles by 1.5 for all the particles whose straight lines intersect on the straight line of the two lines on the diagonal line of the obtained image. As a result, the average grain size of the plate was 100 탆.

(3) Fabrication of Ge-doped gallium nitride self-supporting substrate

(3a) Deposition of seed crystal layer

Subsequently, a seed crystal layer was formed on the processed oriented alumina substrate by MOCVD. Specifically, after depositing a low-temperature GaN layer at 530 占 폚 at 40 nm, a GaN film having a thickness of 3 占 퐉 at 1050 占 폚 was laminated to obtain a seed crystal substrate.

(3b) Deposition of Ge-doped GaN layer by Na flux method

The seed crystal substrate produced in the above process was placed in a bottom portion of an alumina crucible having a flat bottom of a cylinder having an inner diameter of 80 mm and a height of 45 mm and then the melt composition was charged into the crucible in a glove box. The composition of the melt composition is as follows.

Metal Ga: 60 g

Metal Na: 60 g

· Germanium tetrachloride: 1.85 g

The alumina crucible was placed in a container made of heat resistant metal and sealed, and then placed on a stand capable of rotating the crystal growth furnace. After elevating the temperature to 870 ° C and 4.0 MPa in a nitrogen atmosphere, the solution was rotated while being held for 50 hours to grow gallium nitride crystals with stirring. After completion of crystal growth, the mixture was gradually cooled to room temperature over 3 hours, and the growing container was taken out from the crystal growing furnace. Using the ethanol, the melt composition remaining in the crucible was removed, and a sample in which the gallium nitride crystal was grown was collected. In the obtained sample, Ge-doped gallium nitride crystal was grown on the entire surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.5 mm. Cracks were not identified.

The thus-obtained alumina substrate portion of the sample was removed by grinding using a grinding stone to obtain a single piece of Ge-doped gallium nitride. The surface of this Ge-doped gallium nitride crystal was ground by a grinding wheel of # 600 and # 2000 to flatten the surface of the plate, followed by smoothing of the surface of the plate by lapping using diamond abrasive grains to obtain a Ge-doped gallium nitride self- To obtain a substrate. On the other hand, in the smoothing processing, the size of the abrasive grains was gradually reduced from 3 mu m to 0.1 mu m while the flatness was increased. The average roughness (Ra) of the surface of the gallium nitride self-supporting substrate after processing was 0.2 nm.

On the other hand, in this example, an element made of an n-type semiconductor is doped with germanium. However, depending on the use and structure, other elements may be doped or non-doped.

(Evaluation of volume resistivity)

The volume resistivity in the plane of the gallium nitride self-supporting substrate was measured using a Hall effect measuring apparatus. As a result, the volume resistivity was 1 x 10 < ^-2 >

(Evaluation of cross-sectional average diameter of gallium nitride self-standing substrate)

In order to measure the cross-sectional average diameter of the GaN single crystal particles on the outermost surface of the gallium nitride self-supporting substrate, the surface of the self-supporting substrate was photographed with a scanning electron microscope. The visual field range was set to a visual range in which a straight line intersecting with 10 to 30 columnar tissues was drawn when a straight line was drawn on the diagonal line of the obtained image. A straight line of two lines is arbitrarily drawn on the diagonal line of the obtained image and the value obtained by multiplying the average of the lengths of the inner line segments of the individual particles by 1.5 for all the particles whose straight lines intersect is set to Sectional mean diameter of the GaN monocrystalline grains. As a result, the cross-sectional average diameter was about 100 탆. On the other hand, in this example, the interface can be clearly identified on the surface of the scanning microscope, but the above-described evaluation may be performed after the treatment for making the interface stand out by thermal etching or chemical etching.

(4) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

(4a) Deposition of the light-emitting functional layer by MOCVD

An n-GaN layer doped so as to have an Si atom concentration of 5 x 10 ¹⁸ / cm 3 at 1050 캜 was deposited as 1 μm on the gallium nitride self-supporting substrate by the MOCVD method. Subsequently, a multiple quantum well layer was deposited as a light emitting layer at 750 ° C. Specifically, five layers of 2.5 nm well layers made of InGaN and six layers of 10 nm barrier layers made of GaN were alternately laminated. Subsequently, p-GaN doped to 200 nm as a p-type layer was deposited at 950 캜 so that the Mg atom concentration became 1 x 10 ¹⁹ / cm 3. Thereafter, the substrate was taken out from the MOCVD apparatus and subjected to heat treatment at 800 캜 for 10 minutes in a nitrogen atmosphere as an activation treatment of Mg ions in the p-type layer. In order to measure the cross-sectional mean diameter of the single crystal particles on the outermost surface of the light-emitting functional layer, an image was taken by scanning electron microscope on the surface of the light-emitting functional layer. The visual field range was set to a visual range in which a straight line intersecting with 10 to 30 columnar tissues was drawn when a straight line was drawn on the diagonal line of the obtained image. A straight line of two lines is arbitrarily drawn on the diagonal line of the obtained image and a value obtained by multiplying the average of the lengths of the inner line segments of the individual particles by 1.5 for all the particles whose straight lines cross each other is multiplied by Lt; 2 > / cm < 2 > As a result, the cross-sectional average diameter was about 100 탆.

(4b) Fabrication of light emitting device

A Ti / Al / Ni / Au film as a cathode electrode was formed on the surface opposite to the n-GaN layer and the p-GaN layer of the gallium nitride self-supporting substrate by a photolithography process and a vacuum deposition process, , And patterned to a thickness of 60 nm. Thereafter, heat treatment at 700 占 폚 in a nitrogen atmosphere was performed for 30 seconds in order to make good ohmic contact characteristics. Further, a Ni / Au film as a transparent anode electrode was patterned to a thickness of 6 nm and 12 nm, respectively, by using a photolithography process and a vacuum deposition method. Thereafter, heat treatment at 500 占 폚 was carried out in a nitrogen atmosphere for 30 seconds in order to make good ohmic contact characteristics. Further, a Ni / Au film to be an anode electrode pad was patterned to a thickness of 5 nm and a thickness of 60 nm, respectively, on a part of the upper surface of the Ni / Au film as a light-transmitting anode electrode by using a photolithography process and a vacuum deposition method. The thus-obtained wafer was cut into chips, and mounted on a lead frame to obtain a vertical-structured light-emitting device.

(4c) Evaluation of light emitting device

Electric current was applied between the cathode electrode and the anode electrode, and I-V measurement was carried out to confirm the rectifying property. Further, when a forward current was passed through, light emission with a wavelength of 450 nm was confirmed.

Example 2

(1) Fabrication of Mg-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 占 퐉 was laminated on an oriented alumina substrate was produced in the same manner as in (1) to (3) of Example 1. A Mg-doped GaN film was formed on the seed crystal substrate in the same manner as in (3b) of Example 1, except that the melt composition was changed to the following composition.

Metal Ga: 60 g

Metal Na: 60 g

Metal Mg: 0.02 g

In the obtained sample, Mg-doped gallium nitride crystal was grown on the front surface of the 50.8 mm (2 inch) seed crystal substrate, and the thickness of the crystal was about 0.5 mm. Cracks were not identified. The Mg concentration of the obtained gallium nitride was 4 × 10 ¹⁹ / cm 3, and the hole concentration measured using the Hall effect measuring device was 1 × 10 ¹⁸ / cm 3. The aligned alumina substrate portion of the sample thus obtained was removed by grinding with a grinder to obtain a monolith of Mg-doped gallium nitride. The plate surface of the Mg-doped gallium nitride crystal was ground by a grinding wheel of # 600 and # 2000 to flatten the plate surface, followed by smoothing of the plate surface by lapping using diamond abrasive grains to form Mg-doped gallium nitride self- To obtain a substrate. On the other hand, in the smoothing processing, the size of the abrasive grains was gradually reduced from 3 mu m to 0.1 mu m while the flatness was increased. The average roughness (Ra) of the Mg-doped gallium nitride self-supporting substrate surface after processing was 0.2 nm. On the other hand, the cross-sectional average diameter of the Mg-doped gallium nitride self-supporting substrate was measured in the same manner as in Example 1 (3b), and the average cross-sectional diameter was about 100 탆.

(2) Fabrication of light emitting device using Mg-doped gallium nitride self-supporting substrate

(2a) Deposition of p-type layer by MOCVD

P-GaN doped so as to have a Mg atom concentration of 1 x 10 ¹⁹ / cm 3 at 950 캜 was deposited as a p-type layer at 200 nm on the substrate by the MOCVD method. Thereafter, the film was taken out from the MOCVD apparatus and subjected to heat treatment at 800 캜 for 10 minutes in a nitrogen atmosphere as an activation treatment of Mg ions in the p-type layer.

(2b) Formation of n-type layer by RS-MBE method and hydrothermal method

(2b-1) Deposition of the seed crystal layer by the RS-MBE method

Zinc (Zn) and aluminum (Al), which are metal materials, were irradiated with a Krusen cell in an RS-MBE (radical source molecular beam growth) apparatus and supplied to the p-type layer. Oxygen (O), which is a gaseous material, was supplied as an oxygen radical by O ₂ gas as a raw material by an RF radical generator. The purity of various raw materials was 7 N for Zn and 6 N for O ₂ . The substrate was heated to 700 캜 using a resistance heating heater to control the flux of various gas sources so that the Al concentration in the film was 2 x 10 ¹⁸ / cm 3 and the ratio of the concentration of Zn and O atoms was one to one. nm-thick Al-doped n-ZnO.

(2b-2) Deposition of n-type layer by hydrothermal method

Zinc nitrate was dissolved in pure water to a concentration of 0.1 M to obtain Solution A. Subsequently, 1 M ammonia water was prepared to prepare solution B. Subsequently, aluminum sulfate was dissolved in purified water so as to have a concentration of 0.1 M to obtain Solution C. These solutions were mixed and stirred in a volume ratio of A: solution B: solution C = 1: 1: 0.01 to obtain an aqueous solution for growing.

A gallium nitride self-standing substrate on which a seed crystal layer was formed was suspended and placed in one liter of an aqueous solution for growth. Subsequently, a ceramic heater and a magnetic stirrer, which were subjected to waterproofing, were placed in an aqueous solution and hydrothermally treated at 270 ° C for 3 hours in an autoclave to deposit a ZnO layer on the seed crystal layer. The GaN self-supporting substrate on which the ZnO layer was deposited was cleaned and then annealed at 500 ° C in the atmosphere to form an Al-doped n-ZnO layer with a thickness of about 3 μm. No pores or cracks were detected in the sample, and the conductivity of the ZnO layer was confirmed by a tester. The cross-sectional average diameter of the light-emitting functional layer was evaluated using the same method as in Example 1 (4a). As a result, the cross-sectional average diameter of the single crystal particles on the outermost surface of the light-emitting functional layer was about 100 탆.

(2c) Fabrication of light emitting device

Ti / Al / Ni / Au films as cathode electrodes were patterned to thicknesses of 15 nm, 70 nm, 12 nm, and 60 nm, respectively, in the n-type layer using a photolithography process and a vacuum deposition method. The pattern of the cathode electrode was formed into a shape having an opening so that light could be extracted from a portion where no electrode was formed. Thereafter, heat treatment at 700 占 폚 in a nitrogen atmosphere was performed for 30 seconds in order to make good ohmic contact characteristics. Further, a Ni / Au film was patterned as an anode electrode on the surface opposite to the p-GaN layer and the n-ZnO layer of the gallium nitride self-supporting substrate with a thickness of 50 nm and 100 nm, respectively, by using a photolithography process and a vacuum deposition process did. Thereafter, heat treatment at 500 占 폚 was carried out in a nitrogen atmosphere for 30 seconds in order to make good ohmic contact characteristics. The thus-obtained wafer was cut into chips, and mounted on a lead frame to obtain a vertical-structured light-emitting device.

(2d) Evaluation of light emitting device

Electric current was applied between the cathode electrode and the anode electrode, and I-V measurement was carried out to confirm the rectifying property. Further, when a forward current was passed through, a light emission with a wavelength of about 380 nm was confirmed.

Example 3

(1) Fabrication of light-emitting device using Mg-doped gallium nitride self-supporting substrate

(1a) Deposition of the active layer by the RS-MBE method

A Mg-doped gallium nitride self-supporting substrate was prepared in the same manner as in Example 2 (1) and (2a), and 200 nm of p-GaN was deposited as a p-type layer on the substrate. Next, zinc (Zn) and cadmium (Cd), which are metal materials, were irradiated with a Krusen cell in an RS-MBE (radical source molecular beam growth) apparatus and supplied to the p-type layer. Oxygen (O), which is a gaseous material, was supplied as an oxygen radical by O ₂ gas as a raw material by an RF radical generator. The purity of various raw materials was such that Zn, Cd, and O ₂ were 7 N and 6 N, respectively. The substrate was heated to 700 DEG C using a resistance heating heater to form an active layer having a thickness of 1.5 nm while controlling the flux of various gas sources so as to be a Cd _0.2 Zn _0.8 O layer.

(1b) Deposition of n-type layer by sputtering

Next, an n-type ZnO layer was formed to a thickness of 500 nm on the active layer by RF magnetron sputtering. A ZnO target to which Al was added in an amount of 2 parts by weight was used for the film formation, and the film forming conditions were pure Ar atmosphere, pressure of 0.5 Pa, input power of 150 W, and film forming time of 5 minutes. Further, the cross-sectional average diameter of the light-emitting functional layer was evaluated using the same method as in Example 1 (4a). As a result, the average particle size of the light-emitting functional layer was about 100 탆.

(1c) Fabrication of light emitting device

Ti / Al / Ni / Au films as cathode electrodes were patterned to thicknesses of 15 nm, 70 nm, 12 nm, and 60 nm, respectively, in the n-type layer using a photolithography process and a vacuum deposition method. The pattern of the cathode electrode was formed into a shape having an opening so that light could be extracted from a portion where no electrode was formed. Thereafter, heat treatment at 700 占 폚 in a nitrogen atmosphere was performed for 30 seconds in order to make good ohmic contact characteristics. Further, a Ni / Au film was patterned as an anode electrode on the surface opposite to the p-GaN layer and the n-ZnO layer of the gallium nitride self-supporting substrate using a photolithography process and a vacuum deposition process to a thickness of 5 nm and 100 nm, respectively did. Thereafter, heat treatment at 500 占 폚 was carried out in a nitrogen atmosphere for 30 seconds in order to make good ohmic contact characteristics. The thus-obtained wafer was cut into chips, and mounted on a lead frame to obtain a vertical-structured light-emitting device.

(1d) Evaluation of light emitting device

Electric current was applied between the cathode electrode and the anode electrode, and I-V measurement was carried out to confirm the rectifying property. Further, when a forward current was passed through, a light emission with a wavelength of about 400 nm was confirmed.

Example 4

(1) Fabrication of c-plane oriented alumina sintered body

A disk-shaped molded article was obtained in the same manner as in (1) of Example 1. The obtained molded article was placed in a degreasing furnace and degreased under the conditions of 600 占 폚 for 10 hours. The obtained degreased body was fired in a hot press in nitrogen at 1700 占 폚 for 4 hours under a surface pressure of 200 kgf / cm2 using a graphite mold.

The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average grain size of the plate were evaluated in the same manner as in Example 1, and the c-plane orientation degree was 99% and the average particle size was 18 占 퐉.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a 3 mu m-thick GaN film was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in (3b) of Example 1, except that the holding time was 20 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.2 mm. Cracks were not identified.

The surface (surface) of the Ge-doped gallium nitride crystal of the thus-obtained sample was ground using a grinding wheel of # 600 and # 2000 until the thickness of the gallium nitride crystal became about 50 占 퐉 and flattened. Then, The plate surface was smoothed by lapping. Subsequently, the sample was cut to expose the surface in the direction perpendicular to the surface of the substrate, and polished using a CP grinder (IB-09010CP manufactured by Nihon Denshikushi Co., Ltd.), and then subjected to an electron beam backscattering diffraction apparatus (EBSD) ), Reverse mapping of the cross-section of the cross section of the gallium nitride crystal was performed. Figure 2 shows the reverse pole point bearing mapping. In addition, FIG. 3 shows the mapping of the reverse polarity point orientation measured on the plate surface (surface) of the gallium nitride crystal, and FIG. 4 shows the crystal mapping image obtained by enlarging the interface between the oriented alumina substrate and the gallium nitride crystal. 2, the gallium nitride crystal has a larger particle diameter on the surface side (opposite to the oriented alumina substrate) than the oriented alumina substrate side, and the gallium nitride crystal has a shape that is not a complete columnar phase such as a trapezoid or a triangle . In addition, it can be seen that, along with the thickening, the particle size is increased, and the particles whose growth progresses to the surface and the particles whose growth does not proceed to the surface exist. From Fig. 3, it can be seen that each particle constituting the gallium nitride crystal is oriented in the normal direction approximately at the c-plane. It can also be seen from Fig. 4 that the grain of the gallium nitride crystal grows from the crystal grains forming the underlying alumina substrate as the base. It is not clear why the growth behavior accompanied by the increase in the particle diameter is accompanied by the thickening, but as shown in Fig. 5, it is because the growth proceeds in such a manner that particles with a slow growth cover the particles with a slow growth I think. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

Subsequently, the aligned alumina substrate portion of the sample was removed by grinding with a grinding stone to obtain a single piece of Ge-doped gallium nitride. The surface of the Ge-doped gallium nitride crystal was subjected to lapping by diamond abrasive grains on the back surface (the side on which the oriented alumina substrate was in contact), and the back surface (opposite side to the side contacting the oriented alumina substrate) The surface on the side where it was tangent) was smoothed to obtain a GaN self-supporting substrate. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the average cross-sectional surface diameter was about 50 탆, The average diameter was about 18 탆. As described above, the cross-sectional average diameter is larger on the surface side than on the back surface, and the ratio (D _T / D _B ) of the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B on the back surface of the substrate is about 2.8. The aspect ratio of the GaN single crystal grain calculated as the ratio of the thickness of the GaN crystal to the cross-sectional average diameter of the surface was about 1.0.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal particles on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization .

For reference, the surface of the gallium nitride self-supporting substrate prepared in the manner of the above-mentioned (1) and (2) was ground to prepare a self-supporting substrate having a thickness of 20 탆. The ratio of the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the back surface of the substrate (D _T / D _B ) was 1.9 , And the aspect ratio was about 0.6. The above-described light-emitting functional layer was fabricated on the self-orientated oriented GaN crystal, and the current was forwarded in the forward direction after the vertical light-emitting device was turned on. As a result, rectification property and light emission with a wavelength of 450 nm were confirmed, , The luminescence brightness was lower than that of the above-described device.

Example 5

(1) Fabrication of c-plane oriented alumina sintered body

As a raw material, a plate-like alumina powder (grade 02025, manufactured by Kinesei Tech Co., Ltd.), fine alumina powder (grade TM-DAR, manufactured by Daimei Kagaku Kogyo K.K.) and magnesium oxide powder (Ube Material Co., Ltd.), 5 parts by weight of the flaky alumina powder, 95 parts by weight of the fine alumina powder and 0.025 part by weight of the magnesium oxide powder were mixed to obtain alumina raw material. Subsequently, 8 parts by weight of a binder (polyvinyl butyral: part number BM-2, manufactured by Sekisui Chemical Co., Ltd.), 8 parts by weight of a plasticizer (DOP: di (2-ethylhexyl) phthalate , 4 parts by weight of a dispersing agent (LEODOR SP-O30, manufactured by Kao Corporation), 2 parts by weight of a dispersion medium (xylene and 1-butanol in a weight ratio of 1: 1 Were mixed. The amount of the dispersion medium was adjusted so that the slurry viscosity became 20000 cP. The slurry prepared as described above was formed into a sheet form on a PET film by a doctor blade method so as to have a thickness of 100 mu m after drying. The resulting tape was cut into a circular shape with a diameter of 50.8 mm (2 inches), and then 30 sheets were stacked and placed on an Al plate having a thickness of 10 mm, followed by vacuum packing. This vacuum pack was subjected to hydrostatic pressing at a pressure of 100 kgf / cm < 2 > in warm water at 85 DEG C to obtain a disk-shaped molded article.

The obtained molded article was placed in a degreasing furnace and degreased under the conditions of 600 占 폚 for 10 hours. The obtained degreased product was fired in a hot press in nitrogen at 1800 占 폚 for 4 hours under a surface pressure of 200 kgf / cm2 using a graphite mold.

The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average particle size of the plate were evaluated in the same manner as in Example 1, and the degree of c-plane orientation was 96% and the average particle size was about 20 占 퐉.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in Example 1 (3b) except that the holding time was 30 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.3 mm. Cracks were not identified.

The surface (surface) of the Ge-doped gallium nitride crystal of the sample thus obtained was ground using a grinding wheel of # 600 and # 2000 until the thickness of the gallium nitride crystal became about 180 탆 and made flat. Then, The plate surface was smoothed by lapping. Subsequently, the sample was cut to expose the surface in the direction perpendicular to the surface of the substrate, and polished using a CP grinder (IB-09010CP manufactured by Nihon Denshikushi Co., Ltd.), and then subjected to an electron beam backscattering diffraction apparatus (EBSD) ), Reverse mapping of the cross-section of the cross section of the gallium nitride crystal was performed. Figure 6 shows the reverse pole mapping. 6, it can be seen that the gallium nitride crystal has a larger particle diameter on the surface side (opposite to the oriented alumina substrate) than the oriented alumina substrate side, and the gallium nitride crystal has a trapezoidal, triangular, . In addition, it can be seen that, along with the thickening, the particle size is increased, and the particles whose growth progresses to the surface and the particles whose growth does not proceed to the surface exist. The cause of such a behavior is not clear, but it is thought that as shown in Fig. 5, the growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

Subsequently, the aligned alumina substrate portion of the sample was removed by grinding with a grinding stone to obtain a single piece of Ge-doped gallium nitride. The back surface of the Ge-doped gallium nitride crystal (the side facing the oriented alumina substrate) was subjected to lapping by diamond abrasive grains to form a GaN-doped GaN crystal layer on the back surface (opposite to the side in contact with the oriented alumina substrate) And the surface of the GaN substrate was flattened to obtain a 180 mu m thick gallium nitride free-standing substrate. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the cross-sectional average diameter of the surface was about 150 탆, The average diameter was about 20 탆. Thus the average cross-sectional diameter of the back surface side than the ratio (D _T / D _B) of large, average diameter of cross-section of the substrate surface for a cross-sectional average diameter D _B of the back board D _T was about 7.5. The aspect ratio of the GaN single crystal particles calculated as the ratio of the thickness of the GaN crystal to the average cross-sectional surface diameter of the surface was about 1.2.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal grain on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization .

For reference, the surface of the gallium nitride self-supporting substrate prepared in the manner of (1) and (2) above was ground to prepare a self-supporting substrate having a thickness of 50 탆 and a self-supporting substrate having a thickness of 20 탆. Cross-sectional average diameter of the single crystal grain in the outermost surface of the self-standing substrate having a thickness of 50 ㎛ is about 63 ㎛, ratio (D _T / D of the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the substrate back surface _B ) was 3.2, and the aspect ratio was about 0.8. The above-described light-emitting functional layer was fabricated on the self-orientated oriented GaN crystal, and the current was forwarded in the forward direction after the vertical light-emitting device was turned on. As a result, rectification property and light emission with a wavelength of 450 nm were confirmed, , The luminescence brightness was lower than that of the above-mentioned device. Cross-sectional average diameter of the single crystal grain in the outermost surface of the self-standing substrate having a thickness of 20 ㎛ is about 39 ㎛, ratio (D _T / D of the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the substrate back surface _B ) was 2.0, and the aspect ratio was about 0.5. The above-described light-emitting functional layer was fabricated on the self-orientated oriented GaN crystal, and the current was forwarded in the forward direction after the vertical light-emitting device was turned on. As a result, rectification property and light emission with a wavelength of 450 nm were confirmed, , The luminescence brightness was lower than that of the two devices.

Example 6

(1) Fabrication of Ge-doped gallium nitride self-supporting substrate

A c-plane oriented alumina substrate was prepared in the same manner as in Example 5, and a seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated was produced. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in (3b) of Example 1, except that the holding time was 40 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of a 50.8 mm (2 inch) seed crystal substrate, and the thickness of the crystal was about 0.4 mm. Cracks were not identified.

The surface (surface) of the Ge-doped gallium nitride crystal of the sample thus obtained was ground using a grinding wheel of # 600 and # 2000 until the thickness of the gallium nitride crystal became about 260 占 퐉 and flattened. Then, The plate surface was smoothed by lapping. Next, the reverse mapping of the cross-section of the cross section of the gallium nitride crystal was carried out by the same method as in Examples 4 and 5, and the gallium nitride crystal had a larger diameter on the surface side (opposite to the oriented alumina substrate) side than the oriented alumina substrate side , And the shape of the gallium nitride crystal was not a complete columnar shape such as a trapezoid, a triangle, or the like when viewed in cross section. In addition, it was found that there were particles in which the growth progressed to the surface and particles in which the growth did not proceed to the surface, accompanied by increase in particle diameter accompanied with thickening. The cause of such a behavior is not clear, but it is thought that as shown in Fig. 5, the growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

Subsequently, the aligned alumina substrate portion of the sample was removed by grinding with a grinding stone to obtain a single piece of Ge-doped gallium nitride. The back surface of the Ge-doped gallium nitride crystal (the side facing the oriented alumina substrate) was subjected to a lapping process by diamond abrasive grains to form a laminate of the plate surface (opposite to the side contacting the oriented alumina substrate) The side of the side on which the GaN contacted) was smoothed to obtain a GaN self-supporting substrate having a thickness of about 260 mu m. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the average cross-sectional surface diameter was about 220 탆, The average diameter was about 20 탆. Thus the average cross-sectional diameter of the surface side non-(D _T / D _B) of the average cross-section than the diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the large and, if the substrate is was about 11.0. The aspect ratio of the GaN single crystal particles calculated as the ratio of the thickness of the GaN crystal to the average cross-sectional surface diameter of the surface was about 1.2.

(2) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal grain on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization . It was found that the luminescence brightness was somewhat higher but lower than that of Example 5.

Example 7

(1) Fabrication of c-plane oriented alumina sintered body

A c-plane oriented alumina substrate was produced in the same manner as in Example 5 except that the sintering temperature by hot press was 1750 캜. The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average particle size of the plate were evaluated in the same manner as in Example 1, and the degree of c-plane orientation was 96% and the average particle size was 14 占 퐉.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in Example 1 (3b) except that the holding time was 30 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.3 mm. Cracks were not identified.

The surface (surface) of the Ge-doped gallium nitride crystal of the thus-obtained sample was ground using a grinding wheel of # 600 and # 2000 until the thickness of the gallium nitride crystal became about 90 占 퐉 and made flat, The plate surface was smoothed by lapping. Next, the reverse mapping of the cross-section of the cross section of the gallium nitride crystal was performed using the same method as in Examples 4 to 6. As a result, the gallium nitride crystal had a larger diameter on the surface side (opposite to the oriented alumina substrate) side than the oriented alumina substrate side , And the shape of the gallium nitride crystal was not a complete columnar shape such as a trapezoid, a triangle, or the like when viewed in cross section. In addition, it was found that there were particles in which the growth progressed to the surface and particles in which the growth did not proceed to the surface, accompanied by increase in particle diameter accompanied with thickening. The cause of such a behavior is not clear, but it is thought that as shown in Fig. 5, the growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

Subsequently, the aligned alumina substrate portion of the sample was removed by grinding with a grinding stone to obtain a single piece of Ge-doped gallium nitride. The back surface of the Ge-doped gallium nitride crystal (the side facing the oriented alumina substrate) was subjected to a lapping process by diamond abrasive grains to form a laminate of the plate surface (opposite to the side contacting the oriented alumina substrate) (The surface on the side where the GaN layer was in contact with) was smoothed to obtain a GaN self-supporting substrate having a thickness of about 90 mu m (Example 7-1). The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

Further, Ge-doped gallium nitride crystals were prepared in the same manner as described above, and the surface (surface) of the Ge-doped gallium nitride crystal was ground using a grinding wheel of # 600 and # 2000 so that the thickness of the gallium nitride crystal was 70, 50, Respectively, and the plate surface was smoothed by lapping using diamond abrasive grains. Subsequently, the alumina substrate portion was removed as described above, and the back surface of the Ge-doped gallium nitride crystal (the side facing the aligned alumina substrate) was subjected to lapping by diamond abrasive grains to form a plate surface 50, 30, and 20 mu m, respectively, of the back surface (the side opposite to the oriented alumina substrate) and the back surface (the side facing the oriented alumina substrate) were smoothed (Examples 7-2 to 7-5). The average roughness (Ra) of the front and back surfaces of each sample after processing was 0.2 nm.

The volume resistivity of each sample was measured in the same manner as in Example 1 (3), and the volume resistivity was all 1 × 10 ^-2 Ω · cm. The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the thickness of the gallium nitride self- The ratio (D _T / D _B ) of the cross-sectional average diameter of the back surface, the cross-sectional average diameter D _T of the substrate surface to the cross-sectional average diameter D _B of the back surface of the substrate, and the ratio of the thickness of the GaN crystal to the cross- The aspect ratios of the GaN single crystal particles were as shown in Table 1.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal grain on the outermost surface was measured. Further, as a result of fabricating a vertical type light emitting device in the same manner as in Example 1 (4b), the rectifying property was confirmed by IV measurement between any sample and the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm . The luminescence intensities were all somewhat high, but the relationship of Example 7-1> Example 7-2> Example 7-3> Example 7-4> Example 7-5 was satisfied.

Example 8

(1) Fabrication of c-plane oriented alumina sintered body

As a raw material, a flaky alumina powder (grade 02025, manufactured by Kinesei Tech Co., Ltd.), fine alumina powder (grade TM-DAR manufactured by Daimei Kagaku Kogyo K.K.), aluminum fluoride (manufactured by Kanto Kagaku Co., Ltd.) And 5 parts by weight of a flaky alumina powder, 95 parts by weight of a fine alumina powder, 0.05 part by weight of an aluminum fluoride powder and 0.025 part by weight of a magnesium oxide powder were mixed to prepare a magnesium oxide powder (Ube Materialell Co., Ltd., grade 500A) Alumina raw material was obtained. Subsequently, 8 parts by weight of a binder (polyvinyl butyral: part number BM-2, manufactured by Sekisui Chemical Co., Ltd.), 8 parts by weight of a plasticizer (DOP: di (2-ethylhexyl) phthalate , 4 parts by weight of a dispersing agent (LEODOR SP-O30, manufactured by Kao Corporation), 2 parts by weight of a dispersion medium (xylene and 1-butanol in a weight ratio of 1: 1 Were mixed. The amount of the dispersion medium was adjusted so that the slurry viscosity became 20000 cP. The slurry prepared as described above was formed into a sheet form on a PET film by a doctor blade method so as to have a thickness of 100 mu m after drying. The resulting tape was cut into a circular shape with a diameter of 50.8 mm (2 inches), and then 30 sheets were stacked and placed on an Al plate having a thickness of 10 mm, followed by vacuum packing. This vacuum pack was subjected to hydrostatic pressing at a pressure of 100 kgf / cm < 2 > in warm water at 85 DEG C to obtain a disk-shaped molded article.

The obtained molded article was placed in a degreasing furnace and degreased under the conditions of 600 占 폚 for 10 hours. The obtained degreased body was sintered in a nitrogen press at 1800 占 폚 for 4 hours under a pressure of 200 kgf / cm2 using a graphite mold.

The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average particle size of the plate were evaluated in the same manner as in Example 1, and the c-plane orientation degree was 92% and the average particle size was about 64 占 퐉.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in Example 1 (3b) except that the holding time was 30 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.3 mm. Cracks were not identified.

The surface (surface) of the Ge-doped gallium nitride crystal of the thus-obtained sample was ground using a grinding wheel of # 600 and # 2000 until the thickness of the gallium nitride crystal became about 90 占 퐉 and made flat, The plate surface was smoothed by lapping. Then, reverse mapping of the cross-section of the cross-section of the gallium nitride crystal was performed using the same method as in Examples 4 to 7. As a result, the gallium nitride crystal had a larger particle size on the surface side (opposite to the oriented alumina substrate) side than the oriented alumina substrate side , And the shape of the gallium nitride crystal was not a complete columnar shape such as a trapezoid, a triangle, or the like when viewed in cross section. In addition, it was found that there were particles in which the growth progressed to the surface and particles in which the growth did not proceed to the surface, accompanied by increase in particle diameter accompanied with thickening. The cause of such a behavior is not clear, but it is thought that as shown in Fig. 5, the growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

Subsequently, the aligned alumina substrate portion of the sample was removed by grinding with a grinding stone to obtain a single piece of Ge-doped gallium nitride. The surface of the Ge-doped gallium nitride crystal was subjected to lapping by diamond abrasive grains on the back surface (the side on which the oriented alumina substrate was brought into contact) to obtain a roughly 90 Thereby obtaining a gallium nitride self-supporting substrate having a thickness of 탆. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the cross-sectional average diameter of the surface was about 80 탆, The average diameter was about 64 탆. Thus the average cross-sectional diameter of the back surface side than the ratio (D _T / D _B) of large, average diameter of cross-section of the substrate surface for a cross-sectional average diameter D _B of the back board D _T was about 1.3. The aspect ratio of the GaN single crystal grain calculated as the ratio of the thickness of the GaN crystal to the cross-sectional average diameter of the surface was about 1.1.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional diameter of the single crystal grain on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization .

Example 9

(1) Fabrication of c-plane oriented alumina sintered body

A c-plane oriented alumina substrate was produced in the same manner as in Example 8 except that the amount of the aluminum fluoride powder was changed to 0.02 parts by weight. The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average particle size of the plate were evaluated in the same manner as in Example 1, and the c-plane orientation degree was 94% and the average particle size was 41 탆.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in Example 1 (3b) except that the holding time was 30 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.3 mm. Cracks were not identified.

The thus-obtained alumina substrate portion of the sample was removed by grinding using a grinding stone to obtain a single piece of Ge-doped gallium nitride. Subsequently, the back surface of the Ge-doped gallium nitride crystal (the side on which the oriented alumina substrate was in contact) was cut to about 80 탆 using # 600 and # 2000 grindstones. Thereafter, the plate surface (surface) was ground by grinding until the thickness of the gallium nitride crystal became about 60 占 퐉 and flattened. Thereafter, the surface and back surface were flattened by lapping using diamond abrasive grains, To obtain a substrate. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

Then, the reverse mapping of the cross-section of the cross-section of the gallium nitride crystal was carried out by the same method as in Examples 4 to 8. As a result, the grain size of the gallium nitride crystal was larger on the surface side (opposite to the oriented alumina substrate) than on the oriented alumina substrate side , And the shape of the gallium nitride crystal was not a complete columnar shape such as a trapezoid, a triangle, or the like when viewed in cross section. In addition, it was found that there were particles in which the growth progressed to the surface and particles in which the growth did not proceed to the surface, accompanied by increase in particle diameter accompanied with thickening. The cause of such a behavior is not clear, but it is considered that growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth as shown in Fig. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional average diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the average cross-sectional surface diameter was about 81 탆, The average diameter was about 61 탆. Thus the average cross-sectional diameter of the back surface side than the ratio (D _T / D _B) of large, average diameter of cross-section of the substrate surface for a cross-sectional average diameter D _B of the back board D _T was about 1.3. The aspect ratio of the GaN single crystal grain calculated as the ratio of the thickness of the GaN crystal to the cross-sectional average diameter of the surface was about 0.7.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal particles on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization . However, although the luminescence brightness was somewhat high, it was found to be weaker than that of Example 8.

Example 10

(1) Fabrication of c-plane oriented alumina sintered body

As a raw material, a plate-like alumina powder (grade 10030, manufactured by KINSEI TECH CORPORATION), fine alumina powder (grade TM-DAR, manufactured by Daimei Kagaku Kogyo K.K.) and magnesium oxide powder (Ube Material Co., Ltd.), 5 parts by weight of the flaky alumina powder, 95 parts by weight of the fine alumina powder and 0.025 part by weight of the magnesium oxide powder were mixed to obtain alumina raw material. Subsequently, 8 parts by weight of a binder (polyvinyl butyral: part number BM-2, manufactured by Sekisui Chemical Co., Ltd.), 8 parts by weight of a plasticizer (DOP: di (2-ethylhexyl) phthalate , 4 parts by weight of a dispersing agent (LEODOR SP-O30, manufactured by Kao Corporation), 2 parts by weight of a dispersion medium (xylene and 1-butanol in a weight ratio of 1: 1 Were mixed. The amount of the dispersion medium was adjusted so that the slurry viscosity became 20000 cP. The slurry prepared as described above was formed into a sheet form on a PET film by a doctor blade method so as to have a thickness of 100 mu m after drying. The resulting tape was cut into a circular shape with a diameter of 50.8 mm (2 inches), and then 30 sheets were stacked and placed on an Al plate having a thickness of 10 mm, followed by vacuum packing. This vacuum pack was subjected to hydrostatic pressing at a pressure of 100 kgf / cm < 2 > in warm water at 85 DEG C to obtain a disk-shaped molded article.

The obtained molded article was placed in a degreasing furnace and degreased under the conditions of 600 占 폚 for 10 hours. The obtained degreased body was sintered in a nitrogen press at 1800 占 폚 for 4 hours under a pressure of 200 kgf / cm2 using a graphite mold.

The sintered body thus obtained was fixed to a base plate of a ceramics, and the surface of the sintered body was flattened by grinding to # 2000 using a grinding stone. Subsequently, the plate surface was smoothed by lapping using diamond abrasive grains to obtain an oriented alumina sintered body having a diameter of 50.8 mm (2 inches) and a thickness of 1 mm as an oriented alumina substrate. The size of the abrasive grains was gradually reduced from 3 탆 to 0.5 탆, and the flatness was improved. The average roughness (Ra) after processing was 4 nm. The c-plane orientation degree and the average grain size of the plate were evaluated in the same manner as in Example 1, and the c-plane orientation degree was 99% and the average particle size was about 24 탆.

(2) Fabrication of Ge-doped gallium nitride self-supporting substrate

A seed crystal substrate in which a GaN film having a thickness of 3 탆 was laminated on an oriented alumina substrate was produced in the same manner as in (3a) of Example 1. A Ge-doped GaN film was formed on the seed crystal substrate in the same manner as in Example 1 (3b) except that the holding time was 30 hours. In the obtained sample, Ge-doped gallium nitride crystal was grown on the front surface of the seed crystal substrate of 50.8 mm (2 inches), and the thickness of the crystal was about 0.3 mm. Cracks were not identified.

The thus-obtained alumina substrate portion of the sample was removed by grinding using a grinding stone to obtain a single piece of Ge-doped gallium nitride. Subsequently, the back surface of the Ge-doped gallium nitride crystal (the side on which the oriented alumina substrate was in contact) was cut to about 90 탆 by using # 600 and # 2000 grindstones. Thereafter, the plate surface (surface) was ground by grinding until the thickness of the gallium nitride crystal became about 40 占 퐉, and then the surface and the back surface were smoothed by lapping using diamond abrasive grains to form gallium nitride self- To obtain a substrate. The average roughness (Ra) of the front and back surfaces of the GaN self-supporting substrate after processing was 0.2 nm.

Then, reverse mapping of the cross-section of the cross section of the gallium nitride crystal was performed using the same method as in Examples 4 to 9. The gallium nitride crystal had a larger particle size on the surface side (opposite to the oriented alumina substrate) side than the oriented alumina substrate side , And the shape of the gallium nitride crystal was not a complete columnar shape such as a trapezoid, a triangle, or the like when viewed in cross section. In addition, it was found that there were particles in which the growth progressed to the surface and particles in which the growth did not proceed to the surface, accompanied by increase in particle diameter accompanied with thickening. The cause of such a behavior is not clear, but it is thought that as shown in Fig. 5, the growth is progressed in such a manner that particles with a slow growth cover particles with a fast growth. Therefore, among the gallium nitride particles constituting the gallium nitride crystal, the particles exposed on the front surface side communicate with the back surface without passing through the grain boundary, but a part of the particles exposed on the back surface side also includes the growth stopped on the way.

The volume resistivity was measured by the same method as in Example 1 (3), and the volume resistivity was 1 x 10 < ^-2 > The average cross-sectional mean diameter of the GaN single crystal grains on the front and back surfaces of the gallium nitride self-supporting substrate was measured by the same method as in Example 1 (3). As a result, the cross-sectional average diameter of the surface was about 75 탆, The average diameter was about 60 탆. Thus the average cross-sectional diameter of the back surface side than the ratio (D _T / D _B) of large, average diameter of cross-section of the substrate surface for a cross-sectional average diameter D _B of the back board D _T was about 1.3. The aspect ratio of the GaN single crystal grain calculated as the ratio of the thickness of the GaN crystal to the average cross-sectional surface diameter of the surface was about 0.5.

(3) Fabrication of light-emitting device using Ge-doped gallium nitride self-supporting substrate

The light-emitting functional layer was fabricated on the gallium nitride self-supporting substrate in the same manner as in Example 1 (4a), and the average cross-sectional average diameter of the single crystal particles on the outermost surface was measured. Further, as a result of producing a vertical-type light-emitting device in the same manner as in Example 1 (4b), rectification property was confirmed by IV measurement between the cathode electrode and the anode electrode, and light emission with a wavelength of 450 nm was confirmed by forward energization . However, the luminescence brightness was somewhat high, but it was found to be weaker than in Examples 8 and 9.

Example 11

A verification experiment was conducted in order to confirm more clearly that the light-emitting efficiency was remarkably improved when the cross-sectional average diameter of the gallium nitride single crystal grains was 20 μm or more. In this verification experiment, various gallium nitride self-supporting substrates having a cross-sectional mean diameter D _T of 2, 3, 13, 16, 20, 35, 42, 50, 72, 90 and 110 탆 were manufactured as gallium nitride single crystal particles, And the light emission luminance at 200 A / cm 2 (chip size: 1 mm x 1 mm, forward current: 2 A) was measured using LED tester LX4681A manufactured by Technlog Corporation. The results were as shown in Table 2. As is apparent from the results of the luminescence brightness shown in Table 2, when the gallium nitride self-supporting substrate having a cross-sectional mean diameter D _T of 3 to 16 탆 is used, the luminescence brightness is 0.40 to 0.42 (au) It was confirmed that when the gallium nitride self-supporting substrate having a diameter D _T of 20 μm or more was used, the luminescence brightness remarkably increased to 0.91 or more (au). These results clearly show that the luminous efficiency is remarkably improved with the cross-sectional mean diameter of 20 占 퐉 as the boundary.

The present invention includes the following aspects.

[Item 1] A gallium nitride self-standing substrate comprising a plate composed of a plurality of gallium nitride single crystal particles having a single crystal structure in a direction of a normal line.

[Item 2] The gallium nitride self-standing substrate according to item 1, wherein the average diameter of the cross-section of the gallium nitride single crystal particles on the outermost surface of the substrate is 0.3 μm or more.

[Item 3] The gallium nitride self-standing substrate according to item 2, wherein the cross-sectional average diameter is 3 占 퐉 or more.

[Item 4] The gallium nitride self-standing substrate according to item 2, wherein the cross-sectional average diameter is 20 m or more.

[Item 5] A gallium nitride self-standing substrate according to any one of items 1 to 4, having a thickness of 20 m or more.

[Item 6] The GaN self-standing substrate according to any one of Items 1 to 5, having a size of 100 mm or more in diameter.

[Item 7] The gallium nitride self-standing substrate according to any one of items 1 to 6, wherein the gallium nitride monocrystalline grains have a crystal orientation substantially aligned in the normal direction.

[Item 8] The gallium nitride self-standing substrate according to any one of items 1 to 7, wherein the gallium nitride single crystal particle is doped with an n-type dopant or a p-type dopant.

[Item 9] The gallium nitride self-standing substrate according to any one of items 1 to 7, wherein the gallium nitride single crystal particle does not contain a dopant.

[Item 10] The gallium nitride self-standing substrate according to any one of items 1 to 9, wherein the gallium nitride single crystal particles are mixed.

[Item 11] The gallium nitride single crystal substrate according to any one of items 1 to 10, wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride independent substrate are connected to the back surface of the gallium nitride independent substrate through the grain boundaries Gallium nitride self-supporting substrate.

[Item 12] _A method for producing a gallium nitride single crystal, comprising the steps of: forming a gallium nitride single crystal particle exposed on the surface of a gallium nitride single crystal substrate with respect to a cross-sectional average diameter D _B on the outermost surface of the gallium nitride single crystal particle exposed on the back surface of the gallium nitride self- A gallium nitride self-standing substrate according to any one of items 1 to 11, wherein a ratio (D _T / D _B ) of the cross-sectional mean diameter D _{T on} the surface is larger than 1.0.

[Item 13] An aspect ratio, defined as a ratio of the thickness T of the gallium nitride free-standing substrate to the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride independent substrate, (T / D _T ) of the GaN substrate is 0.7 or more.

[Item 14] A GaN substrate as described in any one of items 1 to 13,

Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains formed on the substrate and having a single crystal structure in a substantially normal direction,

Emitting device.

[Item 15] The self-supporting light-emitting device according to item 14, wherein the semiconductor single-crystal particle on the outermost surface of the light-emitting functional layer has an average cross-sectional diameter of 0.3 m or more.

[Item 16] The light-emitting device according to item 15, wherein the cross-sectional average diameter is 3 占 퐉 or more.

[Item 17] A light-emitting device according to any one of items 14 to 16, wherein the semiconductor single crystal particles have a structure in which the crystal orientation of the gallium nitride self-supporting substrate is substantially grown.

[Item 18] The light-emitting device according to any one of items 14 to 17, wherein the light-emitting functional layer is made of a gallium nitride-based material.

[Item 19] A method for manufacturing a semiconductor device, comprising the steps of: preparing an oriented polycrystalline sintered body;

Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation substantially corresponding to the crystal orientation of the oriented polycrystalline sintered body;

Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation substantially corresponding to the crystal orientation of the seed crystal layer;

A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-

Gt; a < / RTI > substrate.

[Item 20] The method according to item 19, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body.

[Item 21] The method according to item 19 or 20, wherein the average particle size of the particles constituting the oriented polycrystalline sintered body on the surface of the substrate is 0.3 to 1000 탆.

[Item 22] The method according to any one of items 19 to 21, wherein the layer composed of the gallium nitride crystal is formed by the Na flux method.

[Item 23] The method according to any one of items 19 to 22, wherein the oriented polycrystalline sintered body has translucency.

[24] A process for preparing the gallium nitride self-supporting substrate described in any one of items 1 to 13, or preparing the gallium nitride self-standing substrate by the method according to any one of items 19 to 23,

At least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a substantially normal direction is formed on the gallium nitride free-standing substrate so as to have a crystal orientation substantially corresponding to the crystal orientation of the gallium nitride substrate, fair

Emitting device.

[Item 25] The method according to item 24, wherein the luminescent functional layer is composed of a gallium nitride-based material.

Claims (46)

Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride independent substrate are formed of a plate composed of a plurality of gallium nitride single crystal particles having a single crystal structure in the normal direction, Sectional surface average diameter D _B on the outermost surface of the gallium nitride single crystal grains exposed on the back surface of the gallium nitride self-supporting substrate without passing through the grain boundaries on the back surface of the gallium nitride self- Wherein the ratio (D _T / D _B ) of the cross-sectional average diameter D _T on the outermost surface of the exposed gallium nitride monocrystalline grains is greater than 1.0. The gallium nitride self-standing substrate according to claim 1, wherein a cross-sectional average diameter of the gallium nitride single crystal particles on the outermost surface of the substrate is 0.3 占 퐉 or more. 3. The gallium nitride self-standing substrate according to claim 2, wherein a cross-sectional average diameter of the gallium nitride-based single crystal particles on the outermost surface of the substrate is 3 占 퐉 or more. The gallium nitride self-standing substrate according to claim 2, wherein the average diameter of the cross-section of the gallium nitride single crystal particles on the outermost surface of the substrate is 20 占 퐉 or more. The gallium nitride self-supporting substrate according to claim 1, having a thickness of 20 탆 or more. The gallium nitride self-supporting substrate according to claim 1, having a size of 100 mm or more in diameter. The gallium nitride self-supporting substrate according to claim 1, wherein the gallium nitride single crystal grain has a crystal orientation aligned in the normal direction. The gallium nitride self-supporting substrate according to claim 1, wherein the gallium nitride single crystal particle is doped with an n-type dopant or a p-type dopant. The gallium nitride self-supporting substrate according to claim 1, wherein the gallium nitride single crystal particle does not contain a dopant. The gallium nitride self-supporting substrate according to claim 1, wherein the gallium nitride single crystal particles are mixed. The gallium nitride self-supporting substrate according to claim 1, wherein the ratio (D _T / D _B ) is 1.5 or more. The gallium nitride single crystal substrate according to claim 1, wherein the ratio of the thickness T of the gallium nitride self-supporting substrate to the cross-sectional average diameter D _T of the top surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride self- Wherein the aspect ratio (T / D _T ) is 0.7 or more. 12. A gallium nitride self-standing substrate as set forth in any one of claims 1 to 12,
Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains having a single crystal structure in the normal direction,
Emitting device. 14. The light emitting device according to claim 13, wherein a cross-sectional average diameter of the semiconductor single crystal particles on the outermost surface of the light-emitting functional layer is 0.3 占 퐉 or more. 15. The light emitting device according to claim 14, wherein a cross-sectional average diameter of the semiconductor single crystal particles on the outermost surface of the light-emitting functional layer is 3 占 퐉 or more. 14. The light emitting device according to claim 13, wherein the semiconductor single crystal grain has a structure grown along the crystal orientation of the gallium nitride self-supporting substrate. 14. The light emitting device according to claim 13, wherein the light emitting function layer is made of a gallium nitride-based material. Preparing an oriented polycrystalline sintered body,
Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation along the crystal orientation of the oriented polycrystalline sintered body;
Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation along the crystal orientation of the seed crystal layer;
A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-
Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride free standing substrate are connected to the back surface of the gallium nitride free standing substrate without passing through the grain boundaries and are exposed on the back surface of the gallium nitride free standing substrate The ratio of the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal grain exposed on the surface of the gallium nitride independent substrate to the cross-sectional average diameter D _B on the outermost surface of the gallium nitride single crystal grain _T / D _B ) is greater than 1.0. The method of manufacturing a gallium nitride self-supporting substrate according to claim 18, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body. 19. The method of producing a gallium nitride self-supporting substrate according to claim 18, wherein the average particle size of the particles constituting the oriented polycrystalline sintered body is 0.3 to 1000 mu m. 19. The method of producing a gallium nitride self-supporting substrate according to claim 18, wherein the layer composed of the gallium nitride crystal is formed by the Na flux method. The method of manufacturing a gallium nitride self-sustaining substrate according to claim 18, wherein the oriented polycrystalline sintered body has translucency. A gallium nitride self-standing substrate according to any one of claims 1 to 12, or a method for manufacturing a gallium nitride self-standing substrate according to any one of claims 18 to 22, ; A step
Forming a light emitting functional layer by forming at least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a normal direction so as to have a crystal orientation along the crystal orientation of the gallium nitride substrate,
Emitting device. The method of manufacturing a light emitting device according to claim 23, wherein the light emitting function layer is made of a gallium nitride-based material. Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride independent substrate are formed of a plate composed of a plurality of gallium nitride single crystal particles having a single crystal structure in the normal direction, Wherein a cross-sectional average diameter of the gallium nitride single crystal grain on the outermost surface of the substrate is not less than 20 占 퐉 and not more than 1000 占 퐉. The gallium nitride self-supporting substrate according to claim 25, wherein said cross-sectional average diameter is not less than 50 탆 and not more than 500 탆. 26. The gallium nitride self-supporting substrate of claim 25, wherein the substrate has a thickness of at least 20 mu m. 26. The gallium nitride self-supporting substrate of claim 25, wherein the substrate has a size of at least 100 mm in diameter. The gallium nitride self-supporting substrate according to claim 25, wherein the gallium nitride single crystal grain has a crystal orientation aligned in the normal direction. The gallium nitride self-supporting substrate according to claim 25, wherein the gallium nitride single crystal particle is doped with an n-type dopant or a p-type dopant. The gallium nitride self-supporting substrate according to claim 25, wherein the gallium nitride-based single crystal particles do not contain a dopant. The gallium nitride self-supporting substrate according to claim 25, wherein the gallium nitride single crystal particles are mixed. The gallium nitride single crystal according to claim 25, wherein the gallium nitride single crystal particles exposed on the back surface of the gallium nitride free standing substrate have an average diameter D _B of the cross section on the outermost surface of the gallium nitride single crystal particles, (D _T / D _B ) of the cross-sectional average diameter D _T at the outermost surface of the gallium nitride substrate is larger than 1.0. 26. The method according to claim 25, wherein the ratio of the thickness T of the gallium nitride self-supporting substrate to the cross-sectional average diameter D _T on the outermost surface of the gallium nitride single crystal particles exposed on the surface of the gallium nitride self- Wherein the aspect ratio (T / D _T ) is 0.7 or more. A method of manufacturing a gallium nitride self-standing substrate according to any one of claims 25 to 34,
Emitting functional layer having at least one layer formed of a plurality of semiconductor single crystal grains having a single crystal structure in the normal direction,
Emitting device. 36. The light emitting device according to claim 35, wherein a cross-sectional average diameter of the semiconductor single crystal particles on the outermost surface of the light-emitting function layer is 20 占 퐉 or more. 37. The light emitting device according to claim 36, wherein a cross-sectional average diameter of the semiconductor single crystal particles on the outermost surface of the light-emitting functional layer is 50 占 퐉 or more. 36. The light emitting device according to claim 35, wherein the semiconductor single crystal grain has a structure grown along the crystal orientation of the gallium nitride self-supporting substrate. 36. The light emitting device according to claim 35, wherein the light emitting function layer is made of a gallium nitride-based material. Preparing an oriented polycrystalline sintered body,
Forming a seed crystal layer made of gallium nitride on the oriented polycrystalline sintered body so as to have a crystal orientation along the crystal orientation of the oriented polycrystalline sintered body;
Forming a layer composed of a gallium nitride crystal having a thickness of 20 占 퐉 or more on the seed crystal layer so as to have a crystal orientation along the crystal orientation of the seed crystal layer;
A step of removing the oriented polycrystalline sintered body to obtain a substrate of gallium nitride self-
Wherein the gallium nitride single crystal particles exposed on the surface of the gallium nitride self-supporting substrate are communicated with the back surface of the gallium nitride self-supporting substrate without passing through grain boundaries, Wherein a cross-sectional average diameter of the single crystal grain is not less than 20 占 퐉 and not more than 1,000 占 퐉. 41. The method of manufacturing a gallium nitride self-supporting substrate according to claim 40, wherein the oriented polycrystalline sintered body is an oriented polycrystalline alumina sintered body. 41. The method of producing a gallium nitride self-sustaining substrate according to claim 40, wherein the average particle size of the particles constituting the oriented polycrystalline sintered body is 0.3 to 1000 mu m. 41. The method of producing a gallium nitride self-supporting substrate according to claim 40, wherein the layer composed of the gallium nitride crystal is formed by the Na flux method. 41. The method of manufacturing a gallium nitride self-sustaining substrate according to claim 40, wherein the oriented polycrystalline sintered body has translucency. A gallium nitride self-standing substrate according to any one of claims 25 to 34, or a method for manufacturing a gallium nitride self-standing substrate according to any one of claims 40 to 44, A step of preparing a substrate,
Forming a light emitting functional layer by forming at least one layer composed of a plurality of semiconductor single crystal particles having a single crystal structure in a normal direction so as to have a crystal orientation along the crystal orientation of the gallium nitride substrate,
Emitting device. The method of manufacturing a light-emitting device according to claim 45, wherein the light-emitting functional layer is made of a gallium nitride-based material.

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