JP5376458B2 - Group III nitride semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III nitride semiconductor containing, as a main component, a composition component expressed by Al<SB>x</SB>Ga<SB>1-x-y</SB>In<SB>y</SB>N (where x and y satisfy 0&le;x, y, 1-x-y&le;1) and oriented in a direction except for the c-axis to inhibit generation of a built-in electric field, for example, in a crystal direction having inversion symmetry. <P>SOLUTION: The semiconductor is oriented in a direction inclined by at least 8&deg; from the c-axis, and contains, as a main component, a composition component expressed by Al<SB>x</SB>Ga<SB>1-x-y</SB>In<SB>y</SB>N (where x and y satisfy 0&le;x, y, 1-x-y&le;1) and contains B by less than 1 atom%. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a group III nitride semiconductor.

Low temperature deposition buffer layer (Non-patent document 1), p-type conductivity control (Non-patent document 2), n-type conductivity control (Non-patent document 3), and manufacturing method of high-efficiency light-emitting layer (Non-patent document 4) High-brightness blue and green using Group III nitride semiconductors that contain the main component of Al _x Ga _1-xy In _y N (0 ≤ x, y, 1-xy ≤ 1) through the accumulation of core technologies White light emitting diodes have already been put into practical use.

  1 and 2 show a typical structure example of a light emitting diode using the group III nitride semiconductor. When using sapphire as the substrate, the low-temperature deposition buffer layer 102 is provided on the sapphire (0001) surface substrate or 101 on the sapphire (11-20) surface substrate, and when using SiC as the substrate, on the SiC (0001) surface substrate 201. N-type GaN: Si layer 103 or 203, GaInN light-emitting layer 104 or 204, p-AlGaN: Mg electron blocking layer 105 or 205, p-GaN: Mg layer 106 or 206 is laminated. Further, 107 or 207 is stacked as an n-layer electrode and 108 or 208 is stacked as a p-layer electrode.

All the heterostructures of Al _x Ga _1-xy In _y N (0 ≤ x, y, 1-xy ≤ 1) light emitting diodes currently in practical use on both sapphire and SiC substrates ( 0001) plane. The biggest reason why the (0001) plane laminated structure is used is that the metal-organic vapor phase epitaxy currently used for fabricating light-emitting elements provides an atomically flat surface that is essential for planar-type element fabrication. It is easy.

Al _x Ga _1-xy In _y N (0 ≤ x, y, 1-xy ≤ 1) Group III nitride semiconductors are promising not only for light-emitting elements, but also for light-receiving elements and electronic elements. All the light receiving elements and electronic elements reported in magazines and the like have a laminated structure on the (0001) plane.

However, Al _x Ga _1-xy In _y N (0 ≦ x, y, 1-xy ≦ 1) group III nitride semiconductor does not have inversion symmetry with respect to the [0001] axis direction, that is, the c axis direction. Therefore, when the crystal structure is distorted, a piezoelectric electric field is generated inside the crystal. Furthermore, spontaneous polarization occurs at the laminated interface due to the material difference. In a light emitting device, the presence of a built-in electric field results in the spatial separation of electrons and holes and reduces the transition probability for luminescence recombination of electrons and holes. Therefore, the light emission efficiency of the light emitting element is reduced as compared with the case without a built-in electric field.

All light-emitting elements using Al _x Ga _1-xy In _y N (0 ≦ x, y, 1-xy ≦ 1) group III nitride semiconductors that are currently in practical use are distorted in the light-emitting layer. And the luminous efficiency is lower than that without distortion. If a heterojunction structure can be formed in a crystal plane orientation with inversion symmetry, a piezoelectric electric field will not be generated even if the crystal is distorted. Therefore, a more efficient light-emitting element than that currently in practical use is realized. There is a possibility.

  On the other hand, as an electronic device, a depletion type field effect transistor has been prototyped using the high-density two-dimensional electrons induced at the laminated interface by the above-described piezoelectric electric field and spontaneous polarization. In addition, with regard to electronic elements, there is a possibility that an enhancement type field effect transistor, which could not be manufactured conventionally, can be realized.

Two methods have been proposed mainly for a laminated structure with crystal plane orientation having inversion symmetry. One uses (0001) or (11-20) planes such as sapphire and SiC as the main plane, and Al _x Ga _1-xy In _y N (0 ≦ x , y, 1-xy ≦ 1) Growing under a crystal growth condition in which an oblique crystal plane other than the (0001) plane of the group III nitride semiconductor, for example, a (10-11) plane facet is formed, In contrast, this is a method for producing a predetermined laminated structure in an oblique direction (Non-Patent Document 5). However, this method has poor reproducibility due to the narrow control range of crystal growth conditions when forming oblique facets other than the (0001) plane, and a highly efficient light emitting device has not been realized so far.

The other is a method using a substrate whose principal surface is other than the (0001) plane.For example, (1) a thick film of GaN (1--) is formed on a LiAlO ₂ (100) plane substrate by using a halogen transport vapor deposition method. (100) surface growth method using the substrate as a substrate (Non-patent Document 6), (2) sapphire partially formed with a dielectric mask, etc. (10-10) A method of forming a laminated structure on a plane or a (10-12) plane substrate (for example, Non-Patent Document 7) has been reported.

  In the method (1), the flatness of the obtained GaN (1-100) surface is inferior, and a high-quality multilayer structure necessary for device fabrication has not been realized. In addition, the method (2) has manufacturing problems such as the need to grow GaN a plurality of times, and a flat layer cannot be obtained unless the film is thicker than 10 μm.

“1986 H. Amano, N. Sawaki, I. Akasaki and Y. Toyoda: Appl. Phys. Lett., 48 (1986) 353” “1989 H. Amano, M. Kito, K. Hiramatsu and I. Akasaki: Jpn. J. Appl. Phys. 28 (1989) L2112” "1991 H. Amano and I. Akasaki: Mat. Res. Soc. Ext Abst., EA-21 (1991) 165)" “1991 N. Yoshimoto, T. Matsuoka, T. Sasaki and A. Katsui, Appl. Phys. Lett., 59 (1991) 2251” “T. Takeuchi, S. Lester, D. Basile, G. Gilorami, R. Twist, F. Mertz, M. Wong, R. Schneider, H. Amano and I. Akasaki, IPAP Conf. Ser., Nitride Semicond. 2000,137 " “E. Kuokstis, C. Q. Chen, M. E. Gaevski, W. H. Sun, J. Wl. Yang, G. Simin, M. A. Khan, H. P, Maruska, D. W. Hill. and M. C. Chou, Appl. Phys. Lett., 81 (2002) 41230 " “2003 C. Chen, J. Yang, H. Wang, J. Zhang, V. Adivarahan, M. Gaevski, E. Kuokstis, Z. Gong, M. Su and M. A. Khan, Jpn. J. Appl. Phys., 42 (2003) L640 "

In the present invention, AlxGa1-x-yInyN (0 ≦ x, y, 0 < 1-xy ≦) oriented in a direction other than the c-axis, for example, a crystal orientation having inversion symmetry to suppress generation of a built-in electric field or the like. It is an object of the present invention to provide a group III nitride semiconductor containing the composition component 1) as a main component.

In order to achieve the above object, the present invention provides:
preparing a sapphire substrate or a 4H-SiC substrate (hereinafter also simply referred to as a SiC substrate) having a principal surface oriented in an orientation inclined at an angle of 8 ° or more from the c-axis;
A film formation process is performed in an atmosphere containing B, and the composition component AlxGa1-x-yInyN (0 ≦ x, y, 0 <1-xy ≦ 1) is included as a main component on the substrate, and B is one atom. Forming a group III nitride semiconductor containing less than% in such a manner that it is oriented in an orientation inclined at least 8 ° from its c-axis;
Obtained by a method for producing a group III nitride semiconductor comprising:
The main surface is oriented in an orientation inclined at least 8 ° from the c-axis, contains as a main component a composition component of AlxGa1-x-yInyN (0≤x, y, 0 <1-xy≤1), and one atom of B The present invention relates to a group III nitride semiconductor, characterized in that the content is less than%.

In order to achieve the above object, the present inventors have conducted intensive studies. As a result, a substrate having a main surface oriented in an orientation inclined by 8 ° or more from the c-axis, such as sapphire or SiC, is prepared, and film formation is performed in the presence of B, whereby the main surface is formed on the substrate. Is capable of epitaxially growing a group III nitride semiconductor containing, as a main component, a composition component of AlxGa1-x-yInyN (0 ≦ x, y, 0 <1-xy ≦ 1) oriented in a direction inclined at least 8 ° from the c-axis I found it.

  As a result, a heterojunction structure can be formed on the substrate at an inclination of 8 ° or more from the c-axis, for example, an orientation having inversion symmetry, and the built-in electric field generated in the group III nitride semiconductor is reduced. And the transition probability for luminescence recombination of electrons and holes can be increased. Therefore, the luminous efficiency can be increased by fabricating a predetermined light emitting device from the group III nitride semiconductor.

  Further, since there is no two-dimensional electron gas due to the piezoelectric electric field, an enhancement type field effect transistor can be obtained.

  The film formation process in the atmosphere containing B is performed, for example, in a state where the substance containing B is arranged in the vicinity of the substrate or in an atmosphere supplied with a gas substance containing B. It can be executed depending on the situation. Furthermore, it can be carried out by using a state in which the substance containing B is vapor-deposited on the substrate in advance, or using an apparatus including an apparatus member made of the substance containing B.

  In any of the cases described above, the atmosphere containing B is set so that a very small amount of B is contained in the group III nitride semiconductor after the film forming process is performed. Specifically, the B content in the group III nitride semiconductor is set to be less than 1 atomic%.

  For example, when the substance containing B is arranged in the vicinity of the substrate, the substance is arranged in an environment that is affected by the film forming process. Specifically, the substance is placed on the susceptor on which the substrate is placed, in an environment where it is exposed to the source gas. In the case where the device member is made of the substance containing B, the susceptor and the inner wall portion in the film forming chamber that receives sufficient heat radiation from the susceptor are made of the substance.

  Further, when supplying the gas substance containing B, the flow rate of the gas substance is appropriately controlled, and when depositing the substance containing B, the thickness of the vapor deposition layer and the group III nitride on the vapor deposition layer The formation temperature of the group III nitride semiconductor is appropriately controlled so that B in the vapor deposition layer is sufficiently diffused into the group III nitride semiconductor when forming the compound semiconductor.

As described above, according to the present invention, AlxGa1-x-yInyN (0 ≦ x, 0) oriented in a direction other than the c axis, for example, a crystal orientation having inversion symmetry, to suppress generation of a built-in electric field or the like. It is possible to provide a group III nitride semiconductor containing a composition component y, 0 < 1-xy ≦ 1) as a main component.

It is a block diagram which shows an example of a light emitting diode. Similarly, it is a block diagram which shows an example of a light emitting diode. It is a block diagram which shows roughly an example of the apparatus used for the manufacturing method of the group III nitride semiconductor of this invention. It is a surface SEM photograph of an AlN / GaN heterostructure. Similarly, it is a surface SEM photograph of an AlN / GaN heterostructure.

  The details of the present invention and other features and advantages will be described in detail below based on the best mode.

  FIG. 3 is a block diagram schematically showing an example of an apparatus used in the method for producing a group III nitride semiconductor of the present invention. In the apparatus shown in FIG. 3, the substrate 301 is placed on the susceptor 303, and the B supply source 302 is arranged in a region close to the substrate 101 on the susceptor 303. The susceptor 303 including the substrate 101 and the B supply source 302 is disposed in a predetermined film formation container 304.

In addition, the film formation container 304 is configured such that TMGa, TMAl, TMIn, NH ₃ , and the like, which are source gases of the group III nitride semiconductor, can be introduced together with a predetermined carrier gas.

  The main surface of the substrate 301 is required to be inclined by 8 ° or more from the c-axis. As such a substrate 301, a sapphire substrate or a SiC substrate is used.

  In addition, the B supply source 302 can simply place a predetermined B-containing substance directly on the susceptor 303, or form a recess in a part of the upper surface of the susceptor 303 and place it in this recess. You can also. Furthermore, a predetermined boat can be prepared and placed in this boat. The B-containing substance may be any of powder, granules, pellets, and blocks, and any form can be appropriately selected and used according to ease of use.

The substrate 301 is heated to a predetermined temperature by the susceptor 303 and supplied with the above-described source gas, whereby AlxGa1-x-yInyN (0 ≦ x, y, 0 < 1) is formed on the substrate 301 based on the principle of the CVD method. The group III nitride semiconductor containing a composition component of −xy ≦ 1) as a main component is formed. At this time, the B supply source is also heated by the susceptor 303. Specifically, since the heating temperature of the substrate 301 by the susceptor 303 is about 400 ° C. to 1200 ° C., the B supply source 302 is also heated to a sufficiently high temperature as the substrate 301 is heated. On the other hand, since the B supply source 302 is also exposed to the source gas, the B-containing material partially evaporates from the B supply source 302 and is supplied onto the substrate 301 during film formation. As a result, the film forming process of the group III nitride semiconductor is performed in an atmosphere containing B in addition to the source gas.

  As a result, formation of the (0001) plane facet of the group III nitride semiconductor on the substrate 301 can be suppressed, and the growth direction of the group III nitride semiconductor can be inclined by 8 ° or more from the c-axis. As a result, it is possible to obtain the group III nitride semiconductor oriented on the substrate 301 in the direction inclined by 8 ° or more from the c-axis.

  Such a group III nitride semiconductor has a small built-in electric field and can increase the transition probability for light-emitting recombination of electrons and holes. Therefore, the luminous efficiency can be increased by fabricating a predetermined light emitting device from the group III nitride semiconductor. Further, since the two-dimensional electron gas due to the piezoelectric electric field is not generated, an enhancement type field effect transistor can be obtained.

In addition, since the group III nitride semiconductor is performed in a B-containing atmosphere, in addition to the composition component AlxGa1-x-yInyN (0 ≦ x, y, 0 < 1-xy ≦ 1) as the main component, B is contained at a ratio of less than 1 atomic%. That is, by arranging the B supply source 302 so that the B content in the group III nitride semiconductor satisfies such a range, the group III nitride is oriented in an orientation inclined at least 8 ° from the c-axis. A semiconductor can be obtained easily.

  Thus, the orientation of the group III nitride semiconductor needs to be inclined by 8 ° or more from its c-axis. As a result, the formation of the (0001) facet can be effectively suppressed, the built-in electric field described above can be reduced more effectively, and the effect of not generating a two-dimensional electron gas can be increased. Can do.

Example 1
In this example, a group III nitride semiconductor was manufactured using a manufacturing apparatus as shown in FIG. First, a (10-12) plane sapphire substrate was prepared, AlN having a thickness of 25 nm was formed on the sapphire substrate at 450 ° C., and GaN having a thickness of 2.0 μm was formed on the AlN at 1050 ° C. As a B supply source, single crystal ZrB ₂ was arranged close to the upstream side of the sapphire substrate.
(Comparative Example 1)
Except that the B supply source was not used, 2.5 nm thick AlN and 2.0 μm nm GaN were formed on the (10-12) plane sapphire substrate in the same manner as in Example 1.

4A is a surface SEM photograph of the AlN / GaN heterostructure obtained in Example 1, and FIG. 4B is a surface SEM photograph of the AlN / GaN heterostructure obtained in Comparative Example 1. In both Example 1 and Comparative Example 1, the orientation direction of the obtained AlN / GaN heterostructure was (1-100) plane. However, as is apparent from FIG. 4, the AlN / GaN heterostructure of Example 1 fabricated using the ZrB ₂ B supply source according to the present invention has a very flat surface, and a high-quality laminated layer for device fabrication. It can be seen that the structure is obtained. On the other hand, in the AlN / GaN heterostructure of Comparative Example 1, the surface flatness is inferior, and it can be seen that a high-quality laminated structure is not obtained in device fabrication.

In addition, when a pn junction structure as shown in FIG. 1 was formed using the AlN / GaN heterostructure obtained in Example 1 to produce a light emitting diode, light emission from the light emitting diode was confirmed. In addition, when a field effect transistor in which ohmic and Schottky electrodes were formed on the AlN / GaN heterostructure obtained in Example 1 was fabricated, the operation of the field effect transistor was confirmed.
(Example 2)
In this example, a group III nitride semiconductor was manufactured using a manufacturing apparatus as shown in FIG. First, a 4H-SiC substrate having a main surface oriented in the (30-38) plane was prepared, and on this SiC substrate, AlN having a thickness of 300 nm and GaN having a thickness of 2.0 μm were formed under the same conditions as in Example 1. Formed.
(Comparative Example 2)
A 300 nm thick AlN and 2.0 μm GaN are formed on a 4H—SiC substrate having a main surface oriented in the (30-38) plane in the same manner as in Example 2 except that the B supply source is not used. did.

  FIG. 5A is a surface SEM photograph of the AlN / GaN heterostructure obtained in Example 2, and FIG. 5B is a surface SEM photograph of the AlN / GaN heterostructure obtained in Comparative Example 2. In Example 2, the orientation direction of the obtained AlN / GaN heterostructure was the same (30-38) plane as the substrate. On the other hand, in Comparative Example 2, the orientation orientation of the obtained AlN / GaN heterostructure includes the same (30-38) plane as that of the substrate, and also includes those oriented in an orientation inclined by 7 ° from the (0001) plane. It was.

Further, as is apparent from FIG. 5, the AlN / GaN heterostructure of Example 2 fabricated using a B source of ZrB ₂ according to the present invention has a very flat surface, and a high-quality stack is produced in the fabrication of the device. It can be seen that the structure is obtained. On the other hand, in the AlN / GaN heterostructure of Comparative Example 2, the surface flatness is inferior, and it can be seen that a high-quality laminated structure is not obtained in device fabrication.

  In addition, when a pn junction structure as shown in FIG. 1 was formed using the AlN / GaN heterostructure obtained in Example 2 to produce a light emitting diode, light emission from the light emitting diode was confirmed. Further, when a field effect transistor in which ohmic and Schottky electrodes were formed on the AlN / GaN heterostructure obtained in Example 2 was fabricated, the operation of the field effect transistor was confirmed.

  As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes are made without departing from the scope of the present invention. It can be changed.

  For example, in the above specific example, the B supply source 302 is disposed in the vicinity of the substrate 301 on which the group III nitride semiconductor is to be formed, so that the film forming process is performed in a B-containing atmosphere. However, the B-containing atmosphere can also be formed by supplying a B-containing gas into the film forming container 304 in addition to the above-described source gas. Further, a B-containing material is previously deposited on the substrate 301, and the temperature at the time of forming the group III nitride semiconductor is appropriately controlled so that B is contained (diffused) in the group III nitride semiconductor being formed. It can also be. Further, an apparatus member, for example, a susceptor 303 may be made of the B-containing material, and the film forming process may be performed in a B-containing atmosphere by appropriately controlling the temperature of the heating to evaporate B. it can.

  Further, in the above specific example, the case where the group III nitride semiconductor is formed by using the CVD method has been described, but other film forming methods can naturally be used.

301 substrate
302 B supply source
303 Susceptor
304 Deposition container

Claims (1)

The main surface is oriented in an orientation inclined at least 8 ° from the c-axis, contains as a main component a composition component of AlxGa1-x-yInyN (0≤x, y, 0 <1-xy≤1), and one atom of B Group III nitride semiconductor, characterized by comprising less than%.