JP2006169024A - Group III nitride crystal, growth method, device and module using the crystal - Google Patents

Abstract

The present invention provides a group III nitride free-standing substrate, a group III nitride semiconductor device, a semiconductor module, and a method for manufacturing the same having high quality, excellent heat dissipation characteristics, and low cost by the flux method.
A group III nitride crystal growth method for growing a group III nitride constituted by reacting the group III metal and the nitrogen from a flux, a mixed melt containing at least a group III metal, and nitrogen. In step (b), an interface for crystal growth of the group III nitride is filled with a melt of at least one of group III metal or flux.
[Selection] Figure 2

Description

  The present invention relates to a group III nitride crystal, a group III nitride semiconductor crystal substrate, a group III nitride semiconductor crystal, a group III nitride semiconductor device, a group III nitride semiconductor crystal grown by a reaction system using an alkali metal and nitrogen Relates to the device.

  Currently, InGaAlN-based (Group III nitride) devices used as purple-blue-green light sources are mainly used for MO-CVD (metal organic chemical vapor deposition) and MBE ( It is manufactured by a crystal growth method using a molecular beam crystal growth method) or the like. When sapphire or SiC is used as a substrate, there are problems such as an increase in crystal defects due to a large difference in thermal expansion coefficient and lattice constant from Group III nitride.

For this reason, it has the fault that device characteristics are bad, for example, it is difficult to lengthen the lifetime of a light emitting device, or operating power becomes large.
Furthermore, when a sapphire substrate is used as the substrate, since this substrate is insulative, it is impossible to take out an electrode from the substrate side as in a conventional light emitting device, and the surface of the nitride semiconductor surface on which the crystal has grown is impossible. It is necessary to take out the electrode from. As a result, there is a problem that the device area becomes large, leading to high costs.

  Further, the group III nitride semiconductor device fabricated on the sapphire substrate is difficult to separate the chip by cleavage, and it is not easy to obtain the resonator end face required for the laser diode (LD) by cleavage. For this reason, at present, resonator end faces are formed by dry etching, or after forming a sapphire substrate to a thickness of 100 μm or less, resonator end faces are formed in a form close to cleavage. In this case as well, it is impossible to easily separate the resonator end face and the chip as in the conventional LD in a single process, resulting in process complexity and cost.

In order to solve these problems, it is desired to use GaN substrates. Thick films are formed on GaAs and sapphire substrates using the HVPE method (hydride vapor phase epitaxy), and these substrates are removed later. Japanese Patent Laid-Open No. 2000-12900 and Patent Document 2 (Japanese Patent Laid-Open No. 2003-178984) propose a method for performing the above.
In addition, the sapphire substrate has low thermal conductivity (42 W / m · K), so it is not suitable for high-power optical devices and electronic devices. The thermal conductivity of GaN crystals is 130 W / m · K, and the GaN substrate is superior to the sapphire substrate in this respect.

However, in order to achieve higher output, a substrate material with higher thermal conductivity is desired.
Non-Patent Document 1 (Japanese Journal of Applied Physics, Vol. 41 (2002) Pt. 2, No. 12B, pp. L1434-1436) realizes higher heat conduction by the following measures. .

1. First, an AlGaN LED structure is formed on a sapphire substrate via a GaN layer, and an Au electrode is formed on the surface.
2. Thereafter, CuW is attached to the LED structure via an Au-based electrode.
3. Thereafter, the sapphire substrate is peeled off by a laser lift-off method using a KrF laser.
4). Further, the GaN layer is removed by polishing.
5. A Ti—Al electrode is formed on one side of the AlGaN-based LED from which the GaN has been removed.

As a result, by turning upside down, a light emitting diode of a CuW substrate is realized (third prior art).
Currently, InGaAlN-based (Group III nitride) devices used as purple-blue-green light sources are mainly used for MO-CVD (metal organic chemical vapor deposition) and MBE ( It is manufactured by crystal growth using molecular beam crystal growth method.

  As a problem when sapphire or SiC is used as a substrate, there is an increase in crystal defects caused by a large difference in thermal expansion coefficient and lattice constant from the group III nitride. For this reason, it leads to the fault that device characteristics are bad, for example, it is difficult to extend the lifetime of the light emitting device, or the operating power is increased.

  Furthermore, in the case of a sapphire substrate, since it is insulative, it is impossible to take out the electrode from the substrate side as in the conventional light emitting device, and it is necessary to take out the electrode from the nitride semiconductor surface side where the crystal has grown. . As a result, there is a problem that the device area becomes large, leading to high costs. Further, the group III nitride semiconductor device fabricated on the sapphire substrate is difficult to separate the chip by cleavage, and it is not easy to obtain the resonator end face required for the laser diode (LD) by cleavage. For this reason, at present, resonator end faces are formed by dry etching, or after forming a sapphire substrate to a thickness of 100 μm or less, resonator end faces are formed in a form close to cleavage. In this case as well, it is impossible to easily separate the resonator end face and the chip as in the conventional LD in a single process, resulting in process complexity and cost.

CuW has a higher thermal conductivity of 190 W / m · K compared to sapphire and GaN substrates, making it suitable for higher-power semiconductor devices. However, in the case of the third prior art, 1 to 5 complicated processes are required, leading to an increase in cost.
On the other hand, the present inventors have been eager to realize a high-quality group III nitride crystal by reacting a mixed melt composed of an alkali metal and a group III metal with a group V raw material containing nitrogen. (For example, JP 2001-058900, JP 2001-064097, JP 2001-64098, JP 2001-102316, JP 2001-119103, JP 2002-128586, JP 2002-128587, JP 2002-201100, JP 2002-326898, JP 2002-338391, JP 2003-012400, JP 2003-081696, JP 2003-160399, JP 2003-238296, JP 2003 206198, JP2003-212696, US Pat. No. 65 Is a method called a flux method disclosed in 2633 Pat.).
Japanese Patent Laid-Open No. 2000-12900 JP 2003-178984 A Japanese Journal of Applied Physics, Vol. 41 (2002) Pt. 2, No. 12B, pp. L1434-1436

  The object of the present invention is to further develop the flux method that has been invented so far, and to improve the heat radiation quality (increase the thermal conductivity) with higher quality than the first prior art and the second prior art. The purpose is that. Furthermore, it is to realize a low cost and high thermal conductivity group III nitride free-standing substrate, a group III nitride semiconductor device, a semiconductor module, and a manufacturing method thereof, which do not lead to a high cost which is a problem in the third conventional technology .

Specifically, an object of claim 1 is to realize a group III nitride crystal of low cost, high quality and high thermal conductivity.
The object of claim 2 is to realize a group III nitride crystal of low cost, high quality and high thermal conductivity.
The purpose of claim 3 is to realize a group III nitride crystal at a lower cost than that of claim 2.
The purpose of claim 4 is to realize a group III nitride crystal having lower cost, higher quality and higher thermal conductivity than those of claims 2 and 3.
The purpose of claim 5 is to realize a group III nitride crystal of low cost, high quality and high thermal conductivity.
An object of claim 6 is to realize a group III nitride crystal at a lower cost than that of claim 2 or claim 3.
The object of claim 7 is to realize a low cost, high quality and high thermal conductivity group III nitride crystal.
An object of the present invention is to realize a low cost, high quality and high thermal conductivity group III nitride semiconductor device.
An object of claim 9 is to realize a low cost, high quality and high thermal conductivity group III nitride semiconductor module.
An object of claim 10 is to realize a group III nitride semiconductor module having higher thermal conductivity than that of claim 9.

  The present invention has been made in order to achieve the above-described object. Specifically, in claim 1, the group III is composed of a flux, a mixed melt containing at least a group III metal, and nitrogen. In a group III nitride crystal growth method for crystal growth of a group III nitride constituted by reacting a metal and nitrogen, at least one of a group III metal or a flux is formed at an interface for crystal growth of the group III nitride. It is characterized by filling the melt.

  Further, according to claim 2, in the group III nitride crystal growth method according to claim 1, the surface of the substrate, the surface of which is made of group III nitride, is uneven, and the surface of the substrate is subjected to III by the above method. It is characterized by growing a group nitride crystal.

  Further, in claim 3, in the group III nitride crystal growth method according to claim 2, the group III nitride is formed on the substrate having a concavo-convex shape formed on the surface of the group III nitride crystal by the method as a substrate. It is characterized by crystal growth.

  Further, according to claim 4, in the group III nitride crystal growth method according to claim 2 or claim 3, after the group III nitride is crystal-grown, an uneven shape is formed on the surface of the group III nitride crystal. It is characterized in that a group III nitride crystal is grown thereon.

  According to a fifth aspect of the present invention, in the group III nitride crystal growth method according to any one of the first to fourth aspects, the crystal growth is performed at a higher growth rate in the plane direction than in the vertical direction of the substrate.

  According to a sixth aspect of the present invention, in the group III nitride crystal growth method according to the third or fourth aspect, the crystal growth step by the flux method and the uneven shape forming step are performed in the same reaction vessel.

  A seventh aspect of the present invention relates to a group III nitride crystal grown using the group III nitride crystal growth method according to any one of the first to sixth aspects.

  Further, claim 8 relates to an invention of a group III nitride semiconductor device manufactured using the group III nitride crystal according to claim 7 as a substrate.

  Claim 9 relates to an invention of a semiconductor module on which the group III nitride semiconductor device according to claim 8 is mounted.

  According to a tenth aspect of the present invention, there is provided a semiconductor module invention characterized in that, among the semiconductor modules according to the ninth aspect, a heat dissipation heat sink is provided in contact with the side surface of the device.

In claim 1, in the reaction vessel, the flux and the substance containing at least a group III metal form a mixed melt, and the mixed melt and the substance containing at least nitrogen are composed of a group III metal and nitrogen. In a group III nitride crystal growth method for crystal growth of group III nitride (hereinafter referred to as a flux method), a group III metal or flux or a mixed flux of group III metal and flux is formed at the interface for group III nitride crystal growth. Since the Group III nitride crystal growth method is characterized by filling with a liquid, a Group III nitride crystal growth method having high quality and high thermal conductivity can be realized at a low cost.
That is, when a crystal is grown by the flux method, a group III nitride crystal is filled with a high thermal conductivity group III metal or flux or a mixed melt of group III metal and flux. It is possible to realize a group III nitride crystal in which a crystal defect in the product crystal terminates in this recess and the crystal defect has a high thermal conductivity. As a result, a complicated process as described in the third prior art is not necessary, leading to cost reduction.

The group III nitride crystal growth method according to claim 1, wherein the surface material is a substrate composed of group III nitride, and the surface of the substrate is uneven, The Group III nitride crystal growth method is characterized by the fact that group III nitride crystals are grown by the flux method at the same time, realizing a high quality and high thermal conductivity group III nitride crystal growth method at low cost. I can do it.
That is, the mixed melt can be held in the concave portion of the substrate surface. As a result, crystal defects in the substrate terminate in the concave portion, and the heat conductivity of the mixed melt is high, so that the heat dissipation is good. It becomes possible to realize a group III nitride crystal. Furthermore, a complicated process as described in the third prior art is not required, leading to cost reduction.

According to a third aspect of the present invention, in the method for growing a group III nitride crystal according to the second aspect, a substrate in which a concavo-convex shape is formed on the surface of a group III nitride crystal by a flux method is used. Since it is a group III nitride crystal growth method characterized by growing a group nitride crystal, it is possible to realize a group III nitride crystal growth method that is low in cost, high quality, and high thermal conductivity.
That is, by forming a concavo-convex shape on the surface of the group III nitride crystal by the flux method, and holding the mixed melt in the concave portion of the substrate surface, crystal defects in the substrate terminate in the concave portion, and the mixed melt Therefore, it is possible to realize a group III nitride crystal with good heat dissipation. Furthermore, a complicated process as described in the third prior art is not required, leading to cost reduction.

According to a fourth aspect of the present invention, in the group III nitride crystal growth method according to the second or third aspect, after the group III nitride crystal is grown by the flux method, the surface of the group III nitride crystal is formed into an uneven shape by the flux method. Is a group III nitride crystal growth method characterized in that a group III nitride crystal is grown on the substrate by a flux method using a substrate formed with a high quality and high thermal conductivity. It is possible to realize a method for growing a group III nitride crystal having a certain rate.
That is, a group III nitride crystal can be grown by the flux method, and a concavo-convex shape can be formed as it is. By holding the mixed melt in the concave portion of the substrate surface, crystal defects in the substrate are terminated at this concave portion and mixed. Due to the high thermal conductivity of the melt, it is possible to realize a group III nitride crystal with good heat dissipation. By growing all the crystals by the flux method, it is possible to grow a high-quality group III nitride crystal with fewer crystal defects. Furthermore, a complicated process as described in the third prior art is not required, leading to cost reduction.

6. The group III nitride crystal growth method according to claim 1, wherein the group III nitride crystal growth method is characterized in that crystal growth is performed at a higher growth rate in the plane direction than in the vertical direction of the substrate. Therefore, it is possible to realize a method for growing a group III nitride crystal that is low in cost, high quality, and high thermal conductivity.
That is, by growing the crystal at a higher growth rate in the plane direction than in the vertical direction of the substrate, a recess can be formed and the mixed melt can be filled in the group III nitride crystal. As a result, a crystal defect in the substrate terminates in this recess, and the heat conductivity of the mixed melt is high, so that a group III nitride crystal with good heat dissipation can be realized. Furthermore, a complicated process as described in the third prior art is not required, leading to cost reduction.

  The group III nitride crystal growth method according to claim 2 or claim 3, wherein the crystal growth step by the flux method and the uneven shape forming step are performed in the same reaction vessel. Since it is a nitride crystal growth method, the cost can be further reduced in addition to the effects of Claim 2 or Claim 3.

  In claim 7, since the group III nitride crystal is grown using the group III nitride crystal growth method according to claim 1 to claim 6, it is a low cost, high quality, high thermal conductivity III. Group nitride crystals can be realized.

Since the group III nitride semiconductor device is manufactured using the group III nitride crystal according to claim 7 as a substrate, the group III nitride semiconductor has low cost, high quality, and high thermal conductivity. A device can be realized.
In other words, a group III nitride crystal with low cost, few crystal defects (high quality), and high thermal conductivity is used as the substrate, so that a device with high output operation and long life can be realized at low cost. .

In claim 9, since it is a semiconductor module mounted with the group III nitride semiconductor device according to claim 8, a group III nitride semiconductor module having low cost, high quality and high thermal conductivity can be realized. .
That is, since a group III nitride crystal device having a low cost, few crystal defects (high quality), and high thermal conductivity is used as a substrate, a high output operation and long life device can be realized at a low cost.

In claim 10, in addition to the function and effect of claim 9, the semiconductor module is characterized in that a heat sink for heat dissipation is provided in contact with the side surface of the device among the semiconductor modules according to claim 9. It becomes possible to realize a group III nitride semiconductor module with better heat dissipation characteristics.
That is, since a group III nitride crystal device having a low cost, few crystal defects (high quality), and high thermal conductivity is used as a substrate, a high output operation and long life device can be realized at a low cost.

According to the first aspect of the present invention, in the reaction vessel, the flux and the substance containing at least a group III metal form a mixed melt, and from the mixed melt and the substance containing at least nitrogen, the group III metal and nitrogen are used. In a group III nitride crystal growth method (hereinafter referred to as a flux method) for growing a group III nitride crystal, a group III metal or a flux or a group III metal and a flux It is a group III nitride crystal growth method characterized by filling a mixed melt.
The flux referred to in the present invention refers to a substance that can be formed at a lower temperature and a lower pressure than a normal reaction temperature and pressure in which a group III nitride is formed only from a group III metal and nitrogen. That is, as the flux, in addition to the group III nitride, an alkali metal such as Li, Na, K, an alkaline earth metal, or a mixture thereof can be used.

  Examples of the substance containing nitrogen include nitrogen gas, azide compounds (for example, sodium azide, potassium azide and other azide compounds and any mixture thereof), and compounds containing nitrogen as a constituent element such as ammonia. B, Ga, Al, In, etc. are applicable as the group III metal (group III compound). Here, boron (B) is not a metal, but as a group III material constituting BN as a group III nitride, in the present invention, the expression group III metal means that a group III compound other than a metal is a group III metal. There is.

The mixed melt used in the present invention may be prepared from the beginning as a substance containing a flux and at least a group III metal, or may form a substance containing a flux and at least a group III metal in the process of crystal growth. Either is fine.
The interface mentioned here is a boundary region between a substrate for growing a group III nitride crystal by the flux method and a crystal grown by the flux method, and an intermediate region when the group III nitride crystal is grown by the flux method. Either can be applied. That is, when a crystal is grown by the flux method, a group III metal crystal or a flux or a mixed melt of a group III metal and a flux is filled in a group III nitride crystal.

The invention according to claim 2 is the group III nitride crystal growth method according to claim 1, wherein the surface material is a substrate composed of group III nitride, and the surface of the substrate is uneven, A group III nitride crystal growth method characterized in that a group III nitride crystal is grown on a substrate surface by a flux method.
The unevenness on the surface of the substrate here is not particularly defined in terms of the formation method and the height of the unevenness, and when a group III nitride is grown on the substrate by the flux method, the flux or flux is applied to the unevenness gap. Any irregularities that can be filled with the contained material can be applied.

  That is, a group III nitride crystal is grown on a concavo-convex substrate by a flux method. At this time, it becomes possible to fill a gap between the irregularities with a group III metal or a flux or a substance containing a mixed melt of a group III metal and a flux.

According to a third aspect of the present invention, there is provided a group III nitride crystal growth method according to the second aspect of the present invention, wherein a substrate is formed by forming a concavo-convex shape on the surface of a group III nitride crystal by a flux method. A group III nitride crystal growth method characterized in that a group III nitride crystal is grown by the above method.
After the group III nitride crystal is grown by the flux method, an uneven shape is formed on the surface of the group III nitride crystal by the flux method, and the group III nitride crystal is used as a substrate according to claim 1 on the substrate. And a group III nitride crystal growth method characterized in that a group III nitride crystal is grown by a flux method.

  In the present invention, as the substrate of claim 2, a group III nitride crystal having a concavo-convex shape formed by a flux method is used. That is, a concavo-convex shape is formed on the surface of the group III nitride by the flux method, and a group III nitride crystal is grown by the flux method using this as a substrate. At this time, the gap between the irregularities is filled with a group III metal or a flux or a substance containing a mixed melt of the group III metal and the flux.

The invention of claim 4 is the method of growing a group III nitride crystal according to claim 2 or claim 3, wherein the group III nitride crystal is grown by the flux method, and then the surface of the group III nitride crystal is formed by the flux method. This is a group III nitride crystal growth method characterized by using a substrate having a concavo-convex shape as a substrate and growing a group III nitride crystal on the substrate by a flux method.
In the present invention, a group III nitride crystal produced by a flux method is used as the substrate according to claim 2 or claim 3. That is, a group III nitride crystal having a concavo-convex shape on its surface is grown by a flux method, and a group III nitride crystal is further grown by a flux method using it as a substrate. At this time, the gap between the irregularities is filled with a group III metal or a flux or a substance containing a mixed melt of the group III metal and the flux.

According to a fourth aspect of the present invention, there is provided the group III nitride crystal growth method according to any one of the first to fourth aspects, wherein the crystal growth is performed at a higher growth rate in the plane direction than in the vertical direction of the substrate. It is a growth method.
The vertical direction of the substrate means a direction substantially perpendicular to the substrate and means that crystals grow upward in the substrate. The surface direction of the substrate is a substantially horizontal direction with respect to the substrate. The fact that the growth rate in the plane direction is faster than the vertical direction means that when the substrate is viewed in cross section, the crystal is likely to grow in the horizontal direction rather than the vertical direction.

  The invention according to claim 6 is the group III nitride crystal growth method according to claim 2 or claim 3, wherein the crystal growth step by the flux method and the step of forming the uneven shape are performed in the same reaction vessel. This is a group III nitride crystal growth method.

  A seventh aspect of the present invention is a group III nitride crystal grown using the group III nitride crystal growth method according to the first to sixth aspects.

  The invention according to claim 8 is a group III nitride semiconductor device manufactured using the group III nitride crystal according to claim 7 as a substrate.

  The invention described in claim 9 is a semiconductor module on which the group III nitride semiconductor device according to claim 8 is mounted.

  A tenth aspect of the present invention is a semiconductor module characterized in that, among the semiconductor modules according to the ninth aspect, a heat sink for heat dissipation is provided in contact with a side surface of the device.

  The present invention will be further described in detail with reference to the following examples. However, these examples are only part of the present invention, and the present invention is a technical idea including these examples.

[Example 1]
A first embodiment will be described with reference to FIGS. The first embodiment relates to claims 1, 2, 5, and 7. FIG. 1 is a cross-sectional view of a group III nitride crystal growth apparatus using a flux method. FIG. 2 shows a substrate having an uneven shape. 3 is a cross-sectional view of a group III nitride crystal grown on the substrate of FIG. 2 using the apparatus of FIG.

There is a second reaction vessel 113 inside the first reaction vessel 101, and a temperature at which the group III nitride can grow crystals between them (inside the first reaction vessel 101 and outside the second reaction vessel 113). A heating device 106 is provided so that it can be controlled. Inside the second reaction vessel 113, a mixed melt holding vessel 102 is installed. In the mixed melt holding container 102, there is a mixed melt 103 composed of Ga as a substance containing at least a group III metal and Na as an alkali metal. There is a lid 109 on the mixed melt holding container 102. There is a slight gap between the mixed melt holding container 102 and the lid 109 so that gas can enter and exit.
A thermocouple 112 for detecting the temperature of the mixed melt holding container 102 is installed in the second reaction container 113. The thermocouple 112 is connected to the heating device 106 so that temperature feedback control is possible.

  For example, nitrogen gas is used as the substance containing at least nitrogen. Nitrogen gas can be supplied from the nitrogen gas container 107 installed outside the first reaction container 101 to the space 108 in the first reaction container and the second reaction container through the gas supply pipe 104. I can do it. In order to adjust the pressure of the nitrogen gas, a pressure adjusting valve 105 is provided. A pressure sensor 111 for detecting the pressure of nitrogen gas in the reaction vessel is installed. At this time, the pressure sensor 111 is fed back to the pressure adjustment valve 105 so that the respective pressures in the first reaction vessel and the second reaction vessel are substantially the same pressure and become a predetermined pressure. It has become.

On the other hand, the substrate shown in FIG. 2 is a GaN (gallium nitride) substrate 110 which is one of group III nitrides. The GaN substrate 110 has a concave portion 201 and a convex portion 202. Further, the crystal defect 203 described in the prior art is present in the GaN substrate and penetrates to the crystal surface. The GaN substrate 110 may be grown by a flux method or may be grown by another method such as VPE or MO-CVD.
A GaN crystal is grown on the GaN substrate 110 of FIG. 2 using the group III nitride crystal growth apparatus by the flux method of FIG. The nitrogen pressure in the reaction vessel of FIG. 1 is set to 4 MPa, the temperature of the mixed melt holding vessel 102 is set to 775 ° C., and the ratio of Na to Ga in the mixed melt 103 is set to 4: 6. A GaN crystal is grown on the GaN substrate 110 (first GaN crystal) by placing the GaN substrate 110 in the mixed melt and maintaining the temperature and pressure in this state.

The GaN crystal newly grown by this flux method is the second GaN crystal 301 in FIG. That is, the second GaN crystal 301 is grown on the GaN substrate 110.
The second GaN crystal 301 grown at this time grows faster in the substrate surface direction (lateral direction in the figure) than in the vertical direction (upward direction in the figure) of the GaN substrate 110. As a result, it is possible to grow the second GaN crystal 301 while leaving the substrate recess 201. Here, the GaN substrate surface is the C plane, that is, the (0001) plane, and the direction perpendicular to the substrate surface is the <0001> direction.

At this time, the recess 201 originally in the substrate is filled with a mixed melt of Ga, which is a Group III metal material, and Na, which is a flux.
Further, the crystal defect 203 penetrates to the surface of the newly grown GaN crystal in the substrate convex portion 202, but terminates at the interface with the filled mixed melt in the substrate concave portion 201. Therefore, the crystal defect density is reduced on the GaN crystal surface newly grown by the flux method.
Further, since the mixed melt is filled, the thermal conductivity in this region is increased, and the heat dissipation characteristics are improved.

  By growing a GaN crystal on the concavo-convex substrate by the flux method in this way, a high-quality GaN crystal having a low defect density and a high thermal conductivity can be obtained without going through the complicated steps described in the prior art. It can be produced. That is, both low cost and high quality can be achieved.

[Example 2]
A second embodiment will be described with reference to FIGS. The second embodiment relates to claims 1, 2, 3, 5, 6, and 7.
FIG. 4 shows a cross section of the GaN substrate 401. The GaN substrate 401 is grown by using a MOVPE method, a HVPE method, or the like, but its manufacturing method is not particularly specified. The GaN substrate 401 has crystal defects 402 penetrating to the crystal surface.
A recess 501 is formed on the surface of the GaN substrate 401 using the apparatus of the flux method shown in FIG. FIG. 5 shows a cross section thereof. Since the description of FIG. 1 is described in the first embodiment, it is omitted here.
First, the GaN substrate 401 shown in FIG. 4 is placed in the mixed melt shown in FIG. Although the GaN crystal 110 is illustrated in FIG. 1, the GaN substrate 401 of FIG.
Using the apparatus of FIG. 1, the temperature of the mixed melt holding container 102 and the nitrogen pressure are set to 900 ° C. and 2 MPa, respectively. By holding the GaN substrate 401 in this state, the recess 501 of the GaN crystal shown in FIG. 5 can be formed. The concave portion 501 of the GaN crystal is generated due to the crystal defect 402.

Next, the temperature of the mixed melt holding container 102 and the nitrogen pressure are set to 775 ° C. and 6 MPa, respectively. By holding the GaN crystal having the recesses in FIG. 5 in this state, the GaN crystal grows thereon. FIG. 6 shows a cross section of the GaN crystal. On the GaN substrate 401 having the recess 501 of FIG. 5, there is a newly grown second GaN crystal 601.
The second GaN crystal 601 grown at this time grows faster in the surface direction of the substrate (horizontal direction in the figure) than in the vertical direction of the GaN substrate 110 (upward direction in the figure). As a result, it is possible to grow the second GaN crystal 601 while leaving the substrate recess 501. Here, the GaN substrate surface is the C plane, that is, the (0001) plane, and the direction perpendicular to the substrate surface is the <0001> direction.
At this time, the concave portion 501 originally in the substrate is filled with a mixed melt 602 of Ga which is a group III metal raw material and Na which is a flux.
Further, the crystal defect 402 terminates at the interface with the mixed melt 602 filled in the substrate recess 501. Therefore, the crystal defect density is reduced on the GaN crystal surface newly grown by the flux method.
Further, since the mixed melt is filled, the thermal conductivity in this region is increased, and the heat dissipation characteristics are improved.

By growing a GaN crystal on the concavo-convex substrate by the flux method, a high-quality GaN crystal having a low defect density and a high thermal conductivity can be obtained without going through the complicated steps described in the prior art. It can be produced. That is, both low cost and high quality can be achieved.
In addition, it is possible to form concavo-convex shapes on GaN crystals by using the flux method equipment and method, and it is possible to realize concavo-convex shape formation, GaN crystal growth, and mixed melt filling with the same equipment at low cost. , Leading to higher quality.

[Example 3]
A third embodiment of the present invention will be described with reference to FIG. This third embodiment relates to claim 1, claim 2, claim 4, claim 5, claim 6 and claim 7.
Crystal growth is performed using the group III nitride crystal growth apparatus according to the flux method of FIG. 1 described in the first and second embodiments. Since the description of FIG. 1 is described in the first embodiment, it is omitted here.
FIG. 7 is a cross section of a GaN crystal grown according to this example.
First, the first GaN crystal 701 is grown using the apparatus of the flux method of FIG. The growth conditions of the first GaN crystal 701 are that the temperature of the mixed melt holding container 102 and the nitrogen pressure in FIG. 1 are 775 ° C. and 4 MPa, respectively. Next, the temperature of the mixed melt holding container 102 is kept at 775 ° C., and the nitrogen pressure is increased to 8 MPa. By doing so, the second GaN crystal 702 grows. At this time, as the nitrogen pressure increases, the growth rate is faster in the surface direction of the substrate (lateral direction in the figure) than in the vertical direction (upward direction in the figure) of the GaN substrate 110. As a result, the third GaN crystal 704 grows on the second GaN crystal 702 while the recess 703 is formed as a region where a part of the GaN crystal does not grow in the lateral direction. Here, the GaN substrate surface is the C plane, that is, the (0001) plane, and the direction perpendicular to the substrate surface is the <0001> direction.

Here, the concave portion 703 is filled with a mixed melt 602 of Ga which is a group III metal raw material and Na which is a flux. Since this mixed melt is filled, the thermal conductivity in this region is increased, and the heat dissipation characteristics are improved.
Further, the GaN crystal grown by the flux method has fewer crystal defects than the GaN crystal formed by the other methods described in the first and second embodiments. As a result, a high-quality GaN crystal having a low defect density and a high thermal conductivity can be produced without going through the complicated steps described in the prior art. That is, both low cost and high quality can be achieved.
In addition, it is possible to form concavo-convex shapes on GaN crystals by using the flux method equipment and method, and it is possible to realize concavo-convex shape formation, GaN crystal growth, and mixed melt filling with the same equipment at low cost. , Leading to higher quality.

[Example 4]
A fourth embodiment of the present invention will be described with reference to FIG. This fourth embodiment relates to claim 8. FIG. 8 is a perspective view of a semiconductor laser which is an application example of the group III nitride semiconductor device of the present invention.
The GaN-based thin films 802 to 707 are grown on the GaN substrate 801 described in the first to third embodiments, in which the density of crystal defects is low and the mixed melt is filled in the recesses. At this time, the inside of the GaN substrate 801 is filled with the mixed melt 811 described in the first, second and third embodiments.
On the GaN substrate 801, an n-type AlGaN layer 802, an n-type GaN layer 803, an InGaN MQW (multiple quantum well) layer 804, a p-type GaN layer 805, a p-type AlGaN layer 806, and a p-type GaN layer 807 are sequentially crystallized. Has grown. As this crystal growth method, a thin film crystal growth method such as MO-VPE (metal organic chemical vapor deposition) method or MBE (molecular beam epitaxy) method is used.

Since these GaN-based thin films 802 to 807 are suitable for thin film growth such as MOVPE and MBE, p-type and n-type conductivity control, carrier concentration control, and mixed crystal composition control of GaN, AlN, InN It is possible to grow a thin film for a device.
As described above, since the crystal defect terminates in the vicinity of the interface with the mixed melt of the concave portion of the GaN crystal, it is very small in the region of the device thin film 802 to 807.
A ridge structure is formed in the laminated film of GaN, AlGaN, and InGaN, and an SiO ₂ insulating film 808 is formed in a state where only the contact region is opened. Electrode Al / Ti 810 is formed.

By injecting current from the p-side ohmic electrode Au / Ni 809 and the n-side ohmic electrode Al / Ti 810 of this semiconductor laser, laser oscillation occurs and laser light is emitted in the direction of the arrow in the figure.
Since this semiconductor laser uses the GaN crystal of the present invention as a substrate, there are few crystal defects in the semiconductor laser device, and since the mixed melt 811 is inside the substrate, the heat dissipation characteristics are good. As a result, a device with a high output operation and a long life can be realized.
In addition, since the GaN substrate is n-type, electrodes can be formed directly on the substrate. When an insulating substrate such as a conventional sapphire substrate is used, two electrodes on the p-side and n-side are formed only from the surface. There is no need to take out, and the cost can be reduced. Furthermore, the light emitting end face can be formed by cleavage, and in combination with chip separation, a low-cost and high-quality device can be realized.

In this embodiment, InGaN MQW is used as the active layer, but the emission wavelength can be shortened using AlGaN MQW as the active layer. Since there are few defects and impurities in the GaN substrate, light emission from a deep order is reduced, and a highly efficient light-emitting device is possible even when the wavelength is shortened.
In this embodiment, application to an optical device has been described. However, application to an electronic device is also applicable to the present invention. In other words, by using a GaN substrate with few defects and excellent heat dissipation characteristics, the GaN-based thin film epitaxially grown on the GaN substrate has few crystal defects, and as a result, leakage current can be suppressed, and the carrier confinement effect in the case of a quantum structure can be achieved. A high performance device with high output and high output can be realized.

[Example 5]
A fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment relates to claims 9 and 10. FIG. 9 is a perspective view of the group III nitride semiconductor module of the present invention.
The group III nitride semiconductor device 903 according to claim 8 of the present invention is mounted on the submount 901. The group III nitride semiconductor device 903 is filled with the mixed melt in the surface direction of the submount 901 shown in FIG.
A heat sink 902 is installed in a direction substantially orthogonal to the submount 901. The heat sink 902 and the group III nitride semiconductor device 903 are mounted at positions where they contact each other.
In this state, when the group III nitride semiconductor device 903 operates, heat is generated, but heat is conducted to the heat sink through the mixed melt inside the group III nitride crystal. At this time, since the thermal conductivity of the mixed melt is high, efficient heat dissipation is possible. As a result, a large output operation of the semiconductor device becomes possible.
The group III nitride semiconductor device described in this embodiment can be applied to any optical device such as a light emitting diode or semiconductor laser, or an electronic device such as a field effect transistor, as long as it is a semiconductor device for high output.

1 is a diagram showing a flux growth crystal apparatus according to Example 1. FIG. 1 is a cross-sectional view of a group III nitride crystal according to Example 1. FIG. 1 is a cross-sectional view of a group III nitride crystal according to Example 1. FIG. 3 is a cross-sectional view of a group III nitride crystal according to Example 2. FIG. 3 is a cross-sectional view of a group III nitride crystal according to Example 2. FIG. 3 is a cross-sectional view of a group III nitride crystal according to Example 2. FIG. 6 is a cross-sectional view of a group III nitride crystal according to Example 3. FIG. 6 is a perspective view of a group III nitride semiconductor device according to Example 4. FIG. 7 is a perspective view of a group III nitride semiconductor module according to Example 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 1st reaction container 102 Mixed melt holding container 103 Mixed melt 104 Gas supply pipe 105 Nitrogen pressure regulating valve 106 Heating device 107 Nitrogen gas container 108 Space in reaction container 109 Lid of mixed melt holding container 110 GaN crystal 111 Pressure sensor 112 Thermocouple 113 Second reaction vessel 201 Concave portion of GaN substrate 202 Convex portion of GaN substrate 203 Crystal defect (dislocation)
301 Second GaN crystal 401 GaN substrate 402 Crystal defect (dislocation)
501 Concave part of GaN crystal 601 Second GaN crystal 602 Mixed melt 701 First GaN crystal 702 Second GaN crystal 703 Concave part 704 Third GaN crystal 801 n-type GaN substrate 802 n-type AlGaN clad layer 803 n-type GaN Guide layer 804 InGaN MQW active layer 805 p-type GaN guide layer 806 p-type AlGaN cladding layer 807 p-type GaN contact layer 808 SiO ₂ insulating film 809 p-side ohmic electrode 810 n-side ohmic electrode 811 mixed melt 901 submount 902 heat sink 903 Group III nitride semiconductor devices

Claims (10)

In the group III nitride crystal growth method of growing a group III nitride constituted by reacting the group III metal and the nitrogen from a flux and a mixed melt containing at least a group III metal and nitrogen,
A Group III nitride crystal growth method, wherein an interface for crystal growth of the Group III nitride is filled with a melt of at least one of a Group III metal or a flux.   2. The group III nitride crystal growth method according to claim 1, wherein the surface of the substrate made of group III nitride is uneven, and the group III nitride crystal is grown on the substrate surface by the method. A method for growing a group III nitride crystal characterized by comprising:   3. The group III nitride crystal growth method according to claim 2, wherein the group III nitride crystal is grown by the method on the substrate having a concavo-convex shape formed on the surface of the group III nitride crystal by the method as a substrate. Group III nitride crystal growth method.   4. The group III nitride crystal growth method according to claim 2 or 3, wherein the group III nitride is formed on the substrate having a concavo-convex shape formed on the surface of the group III nitride crystal after crystal growth of the group III nitride. A method for growing a group III nitride crystal, characterized by growing a crystal.   5. The group III nitride crystal growth method according to claim 1, wherein the crystal growth is performed at a higher growth rate in the plane direction than in the vertical direction of the substrate.   5. The group III nitride crystal growth method according to claim 3 or 4, wherein the crystal growth step by a flux method and the step of forming an uneven shape are performed in the same reaction vessel. Method.   A group III nitride crystal grown using the group III nitride crystal growth method according to claim 1.   A group III nitride semiconductor device produced using the group III nitride crystal according to claim 7 as a substrate.   A semiconductor module on which the group III nitride semiconductor device according to claim 8 is mounted.   10. A semiconductor module according to claim 9, further comprising a heat sink for heat dissipation that is in contact with a side surface of the device.

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