JP5549157B2 - GaN single crystal substrate and manufacturing method thereof, and GaN-based semiconductor device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a GaN single crystal substrate having a large diameter, a plane orientation of the main surface other than (0001) and (000-1) (ie {0001}), and a substantially uniform carrier concentration distribution in the main surface; It relates to the manufacturing method. The present invention also relates to a GaN-based semiconductor device in which at least one GaN-based semiconductor layer is formed on the main surface of the GaN single crystal substrate and a method for manufacturing the same.

  Group III nitride crystals suitably used for light emitting devices, electronic devices, semiconductor sensors, etc. are usually vapor phase methods such as HVPE (hydride vapor phase epitaxy) and MOCVD (metal organic chemical vapor deposition), flux methods The crystal is grown on a main surface such as a sapphire substrate having a (0001) principal surface or a (111) A principal surface by a liquid phase method. For this reason, the group III nitride crystal usually obtained has a main surface with a plane orientation of {0001}.

  A light-emitting device in which a light-emitting layer having an MQW (multiple quantum well) structure is formed on a main surface of a group III nitride crystal having a main surface of {0001} in the plane orientation has a group III nitride crystal < Since the polarization in the 0001> direction causes spontaneous polarization in the light emitting layer, the blue shift of light emission becomes large and the light emission efficiency decreases. For this reason, a group III nitride crystal having a principal surface with a plane orientation other than {0001} is desired.

  In order to respond to such a request, Japanese Patent Application Laid-Open No. 2008-143772 (hereinafter referred to as Patent Document 1) describes {1-10X} (where X is an integer equal to or greater than 0), {11-2Y} (where Y Is an integer greater than or equal to 0) and {HK− (H + K) 0} (where H and K are integers other than 0), the plane orientation with an off angle of 5 ° or less, specifically { 1-100}, {11-20}, {1-102}, {11-22}, {12-30}, and a group III nitride crystal having a principal plane of any one of {23-50} The manufacturing method is disclosed.

  However, even when the manufacturing method disclosed in Patent Document 1 is used, the group III nitride crystal grown on the principal plane having the {1-100}, {11-20} or {23-50} plane orientation is partially Therefore, there is a problem that it is difficult to obtain a large-diameter single crystal substrate. Further, a crystal growth surface of a group III nitride crystal grown on a {1-102}, {11-22} principal plane has a facet of {0001} and a plane other than {0001}. Orientation facets arise. Here, the impurity uptake efficiency in the facets having the {0001} plane orientation is greatly different from the impurity uptake efficiency in the facets having a plane orientation other than {0001}. For this reason, there is a problem that the variation in the characteristics of the semiconductor device using such a substrate becomes large because the variation in the carrier concentration and the specific resistance on the main surface of the grown group III nitride crystal is large.

  JP-A-2005-101475 (hereinafter referred to as Patent Publication 2) discloses a group III-V nitride semiconductor substrate (specifically, a GaN free-standing substrate) having a substantially uniform carrier concentration distribution and its manufacture. A method is disclosed. However, Patent Document 2 discloses that a carrier concentration distribution becomes substantially uniform by flattening crystal growth in a group III-V nitride semiconductor substrate having a main surface with a plane orientation of (0001). Although it is disclosed, there is no description or suggestion that the carrier concentration distribution is substantially uniform in the group III-V nitride-based semiconductor substrate having a main surface with a plane orientation other than {0001}.

JP 2008-143772 A JP 2005-101475 A

  The present invention solves the above-mentioned problems, and has a large diameter, the surface orientation of the main surface is other than (0001) and (000-1), and the carrier concentration distribution in the main surface is substantially uniform. And it aims at providing the manufacturing method. Another object of the present invention is to provide a GaN-based semiconductor device having at least one GaN-based semiconductor layer formed on the main surface of the GaN single crystal substrate and having a uniform characteristic distribution and a method for manufacturing the same. .

In the present invention, the area of the main surface is 10 cm ² or more, the surface orientation of the main surface is inclined at 72 ° or more and 78 ° or less with respect to the (0001) plane or the (000-1) plane, The GaN single crystal substrate has a carrier concentration variation of within ± 50% of the average carrier concentration in the main surface.

In the GaN single crystal substrate according to the present invention can be within 50% ± with respect to the average resistivity of the main surface variation of resistivity in the main plane. Furthermore, the average specific resistance in the main surface can be 0.1 Ωcm or less.

The present invention is also a method for producing the above GaN single crystal substrate, wherein the main surface has an area of 10 cm ² or more and the surface orientation of the main surface is 72 with respect to the (0001) plane or the (000-1) plane. A step of preparing a GaN seed crystal substrate inclined at an angle of not less than 78 ° and not more than 78 °, a step of growing a GaN single crystal on the main surface of the GaN seed crystal substrate, and a GaN single crystal on the main surface of the GaN seed crystal substrate And a step of cutting a parallel plane to form a GaN single crystal substrate.

  The present invention is also a GaN-based semiconductor device including the GaN single-crystal substrate and at least one GaN-based semiconductor layer formed on the main surface of the GaN single-crystal substrate.

  The present invention also provides a method for manufacturing a GaN-based semiconductor device, comprising: preparing the GaN single-crystal substrate as described above; and growing at least one GaN-based semiconductor layer on the main surface of the GaN single-crystal substrate. It is.

  According to the present invention, there is provided a GaN single crystal substrate having a large diameter, a plane orientation of the main surface other than (0001) and (000-1) and a substantially uniform carrier concentration distribution in the main surface, and a method for manufacturing the same. Can be provided. In addition, it is possible to provide a GaN-based semiconductor device having at least one GaN-based semiconductor layer formed on the main surface of the GaN single crystal substrate and having a uniform characteristic distribution and a method for manufacturing the same.

It is the schematic which shows an example of the GaN single crystal substrate concerning this invention. It is the schematic which shows an example of the manufacturing method of the GaN single crystal substrate concerning this invention. Here, (A) shows a step of cutting a plurality of GaN mother crystal pieces from the GaN mother crystal, and (B) shows a GaN seed crystal substrate by arranging a plurality of GaN mother crystal pieces adjacent to each other in the lateral direction. (C) shows a step of growing a GaN single crystal, and (D) shows a step of forming a GaN single crystal substrate. It is a schematic sectional drawing which shows the other example of the manufacturing method of the GaN single crystal substrate concerning this invention. Here, (A) shows a step of preparing a GaN seed crystal substrate, (B) shows a step of growing a GaN single crystal, and (C) shows a step of forming a GaN single crystal substrate. It is a schematic diagram which shows the condition of the inclination of the surface orientation of the main surface with respect to (0001) plane or (000-1) plane in the GaN single crystal substrate concerning this invention. Here, (A) shows the case where the surface orientation of the main surface is {20-21}, (B) shows the case where the surface orientation of the main surface is {20-2-1}, and (C) shows the main surface orientation. The case where the surface orientation of the surface is {22-42} is shown, and (D) shows the case where the surface orientation of the main surface is {22-4-2}. 1 is a schematic sectional view showing an example of a GaN-based semiconductor device according to the present invention.

In crystal geometry, a display (mirror display) such as (hkl) or (hkil) is used to indicate the plane orientation of the crystal plane. Plane orientation of the crystal plane in the hexagonal crystal system crystal such as III-nitride crystal to form a etc. GaN seed crystal substrate and a GaN single crystal substrate is represented by (hkil). Here, h, k, i and l are integers called Miller indices and have a relationship of i = − (h + k). The plane having the plane orientation (hkil) is referred to as the (hkil) plane. The direction perpendicular to the (hkil) plane (the normal direction of the (hkil) plane) is referred to as the [hkil] direction. Also, {hkil} means a generic plane orientation including individual plane orientations equivalent to (hkil) and its crystal geometry, and <hkil> is equivalent to [hkil] and its crystal geometry It means a generic direction including individual directions.

  Here, in a group III nitride crystal such as a GaN seed crystal and a GaN single crystal, group III element atomic planes such as gallium (Ga) atomic planes and nitrogen (N) atomic planes are alternately arranged in the <0001> direction. , <0001> direction is polar. In the present application, the crystal axes are set so that the group III element atomic plane such as the gallium atomic plane is the (0001) plane and the nitrogen atomic plane is the (000-1) plane.

[GaN single crystal substrate]
(Embodiment 1)
Referring to FIG. 1, a GaN single crystal substrate 20p according to an embodiment of the present invention has an area of a main surface 20pm of 10 cm ² or more, and the surface orientation of the main surface 20pm is a (0001) plane or (000-1). ) It is inclined at 65 ° or more and 85 ° or less with respect to the surface 20c, and the carrier concentration distribution in the main surface 20pm is substantially uniform.

The GaN single crystal substrate 20p of the present embodiment has a large diameter with an area of the main surface 20pm of 10 cm ² or more. Moreover, since the plane orientation of the main surface 20pm has an inclination angle α of 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane 20c, the GaN single crystal substrate 20p is used. For GaN-based semiconductor devices, the blue shift of light emission is suppressed, and the decrease in light emission efficiency is suppressed. From such a viewpoint, the plane orientation of the main surface 20pm preferably has an inclination angle α of 70 ° or more and 80 ° or less with respect to the (0001) plane or the (000-1) plane 20c, and is 72 ° or more. More preferably, it has an inclination angle α of 78 ° or less. Further, since the carrier concentration distribution in the main surface 20pm is substantially uniform, the distribution of device characteristics in the main surface of the GaN-based semiconductor device using the GaN single crystal substrate 20p is substantially uniform. Become.

  In the GaN single crystal substrate 20p of the present embodiment, the distribution of carrier concentration in the main surface 20pm is substantially uniform means that the distribution of device characteristics in the main surface of a GaN-based semiconductor device using the substrate is substantially uniform. For example, the carrier concentration variation within the main surface 20 pm is within ± 50% of the average carrier concentration within the main surface 20 pm. From the viewpoint of making the distribution of device characteristics in the main surface of the GaN-based semiconductor device more uniform, the carrier concentration variation in the main surface 20pm is within ± 30% of the average carrier concentration in the main surface 20pm. Is preferred. Here, the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p can be measured at a 2 mm pitch in the two-dimensional direction in the main surface 20pm by, for example, the van der Pauw method.

  In the GaN single crystal substrate 20p of the present embodiment, it is preferable that the specific resistance distribution in the main surface 20pm is substantially uniform from the viewpoint of uniform distribution of device characteristics. Here, the distribution of specific resistance at 20 pm in the main surface being substantially uniform means that the distribution of device characteristics in the main surface of a GaN-based semiconductor device using the same is substantially uniform. For example, it means that the variation of the specific resistance within the main surface 20 pm is within ± 50% with respect to the average specific resistance within the main surface. From the viewpoint of making the distribution of device characteristics in the main surface of the GaN-based semiconductor device more uniform, the variation in specific resistance within the main surface 20 pm is within ± 30% of the average specific resistance within the main surface 20 pm. Is preferred. Here, the specific resistance in the main surface 20pm of the GaN single crystal substrate 20p can be measured at a 2 mm pitch in the two-dimensional direction in the main surface 20pm by, for example, the van der Pauw method.

[Method of manufacturing GaN single crystal substrate]
(Embodiment 2)
2 and 3, the method for manufacturing a GaN single crystal substrate according to one embodiment of the present invention is a method for manufacturing GaN single crystal substrate 20p according to Embodiment 1, and the area of main surface 10pm is 10 cm. A step of preparing a GaN seed crystal substrate 10p having a surface orientation of ² or more and an inclination of 65 to 85 ° with respect to the (0001) plane or the (000-1) plane 1c (FIG. 2 ( (A) to (B), FIG. 3 (A)), a step of growing the GaN single crystal 20 on the main surface 10pm of the GaN seed crystal substrate 10p (FIGS. 2C and 3B), GaN A step (FIGS. 2D and 3C) of cutting the single crystal 20 along planes 20u and 20v parallel to the main surface 10pm of the GaN seed crystal substrate 10p to form a GaN single crystal substrate. The manufacturing method of the GaN single crystal substrate of this embodiment can efficiently manufacture the GaN single crystal substrate of Embodiment 1 by including such steps.

(Example I of Embodiment 2)
With reference to FIG. 2, an example (hereinafter referred to as Example I) of the method for manufacturing a GaN single crystal substrate of the present embodiment is as follows.
Referring to FIGS. 2A and 2B, in Example I, the step of preparing GaN seed crystal substrate 10p is performed from GaN mother crystal 1 to (0001) plane or (000-1) plane 1c. A sub-process (FIG. 2A) for cutting out a plurality of GaN mother crystal pieces 1p having a principal surface 1pm having a plane orientation inclined at an inclination angle α of 65 ° to 85 °, and a plurality of GaN mother crystal pieces 1p Are disposed adjacent to each other in the lateral direction so that the principal surfaces 1pm of the mother crystal pieces are parallel to each other and the [0001] directions of the mother crystal pieces are parallel to each other. A GaN seed crystal in which the area of 10 pm is 10 cm ² or more and the plane orientation of the main surface 10 pm is inclined at an inclination angle α of 65 ° or more and 85 ° or less with respect to the (0001) plane or (000-1) plane 1c. Sub-process for forming the substrate 10p (FIG. 2) Includes a B)), the.

  First, referring to FIG. 2A, in a sub-process of cutting out a plurality of GaN mother crystal pieces 1p, from GaN mother crystal 1 to (0001) plane or (000-1) plane 1c of GaN mother crystal 1 A plurality of GaN mother crystal pieces 1p are cut out on a plane parallel to the plane orientation {hkil} inclined at an inclination angle α of 65 ° to 85 ° (a plane perpendicular to the <hkil> direction). Here, the inclination angle α can be measured by an X-ray diffraction method.

  The GaN seed crystal used in the above process is not particularly limited, and is an ordinary method, that is, a vapor phase method such as HVPE (hydride vapor phase epitaxy) method or MOCVD (metal organic chemical vapor deposition) method, a flux method, or the like. According to the liquid phase method, it is sufficient to be produced by crystal growth on a main surface such as a sapphire substrate having a (0001) main surface or a GaAs substrate having a (111) A main surface. Therefore, although this GaN mother crystal 1 is not particularly limited, it usually has a (0001) main surface. This GaN mother crystal 1 has facets formed on the crystal growth surface (crystal growth surface) as disclosed in JP-A-2001-102307 from the viewpoint of reducing dislocation density and increasing crystallinity. The crystal growth is preferably performed without embedding the facet, and the growth is preferably performed by a facet growth method.

  Moreover, there is no restriction | limiting in particular in the method of cutting out the some GaN mother crystal piece 1p from the GaN mother crystal 1, Various methods, such as a wire saw, an inner peripheral blade, an outer peripheral blade, or a laser, can be used.

  Further, from the viewpoint of growing the highly crystalline GaN single crystal 20, the average roughness Ra of the main surface 1pm and the side surfaces of the plurality of GaN mother crystal pieces 1p is preferably 50 nm or less, and more preferably 5 nm or less. The average surface roughness Ra means the arithmetic average roughness Ra specified in JIS B 0601-1994. Specifically, the surface is extracted by a reference length in the direction of the average line from the roughness curve, and This is the value obtained by summing the distances from the average line to the roughness curve (absolute value of deviation) and averaging them with the reference length. The average surface roughness Ra can be measured using an AFM (Intermolecular Force Microscope) or the like.

  In order to set the average roughness Ra of the main surface 1pm and side surfaces of the plurality of GaN mother crystal pieces 1p to preferably 50 nm or less, more preferably 5 nm or less, the plurality of GaN mother crystal pieces 1p that are cut out are It is preferable that the surface 1pm and the side surface are ground and / or polished. Polishing includes mechanical polishing, CMP (chemical mechanical polishing), and the like.

Next, referring to FIG. 2B, in the sub-step of forming GaN seed crystal substrate 10p, the plurality of GaN mother crystal pieces 1p cut out have main surfaces 1pm of the mother crystal pieces parallel to each other, In addition, by arranging them in the lateral direction so as to have the same [0001] direction of the mother crystal pieces, the area of the main surface 10 pm is 10 cm ² or more, and the plane orientation of the main surface 10 pm is A GaN seed crystal substrate 10p is formed that is inclined at 65 ° to 85 ° with respect to the (0001) plane or the (000-1) plane 1c.

  The plurality of GaN mother crystal pieces 1p have a GaN seed crystal substrate if the angle formed between the principal surface 1pm of the mother crystal pieces and the crystal axis is not uniform within the principal surface 10pm of the GaN seed crystal substrate 10p formed as described above. Since the chemical composition of the GaN single crystal grown on the main surface 10pm of 10p becomes non-uniform in the plane parallel to the main surface 10pm of the GaN seed crystal substrate 10p, the main surfaces 1pm of the mother crystal pieces are parallel to each other. It arrange | positions so that it may become. It is sufficient that the main surfaces 1pm of these mother crystal pieces are parallel to each other, and they do not necessarily have to be on the same plane. However, the height difference ΔT (not shown) between the main surfaces 1pm of two adjacent GaN mother crystal pieces 1p is preferably 0.1 mm or less, and more preferably 0.01 mm or less.

  Further, from the viewpoint of achieving more uniform crystal growth by making the crystal orientations of the mother crystal pieces the same, the plurality of GaN mother crystal pieces 1p are arranged so that the [0001] directions of the mother crystal pieces are the same. Arranged in the direction. The plurality of GaN mother crystal pieces 1p are arranged adjacent to each other because there is a gap between the substrates and the crystallinity of crystals growing on the gaps is reduced.

  Next, referring to FIG. 2C, in the step of growing the GaN single crystal 20 on the main surface 10pm of the GaN seed crystal substrate 10p, the method of growing the GaN single crystal 20 is not particularly limited. From the viewpoint of epitaxially growing a GaN single crystal, a gas phase method such as HVPE method or MOCVD method, a liquid phase method such as flux method, or the like is preferably used. Among the crystal growth methods, the HVPE method is preferable from the viewpoint of high crystal growth rate.

When the GaN single crystal 20 is grown on the main surface 10pm of the GaN seed crystal substrate 10p, the crystal growth surface 20g of the GaN single crystal 20 is parallel to the main surface 10pm of the GaN seed crystal substrate 10p when viewed macroscopically. When viewed microscopically, a plurality of facets 20fa and 20fb that are not parallel to the main surface 10pm of the GaN seed crystal substrate 10p are formed. The plurality of facets 20fa and 20fb have different plane orientations. That, GaN single crystal 20 is grown plane orientation different from each other a plurality of facet bets 2 0FA, the 20fb as a crystal growth surface 20g. Here, since the facet 20fa and the facet 20fb have different plane orientations, the impurity concentrations incorporated in these facets are different. Therefore, the GaN single crystal 20 grown on the main surface 10pm of GaN seed crystal substrate 10p is, variation in the carrier concentration in a plane parallel to the main surface 10pm of Ga N seed crystal substrate 10p.

  At this time, if the inclination with respect to the (0001) plane or the (000-1) plane 1c in the plane orientation of the main surface 10pm of the GaN seed crystal substrate 10p is small, for example, if the inclination angle α is smaller than 65 °, the main surface 10pm. A facet 20fa having a plane orientation of (0001) or (000-1) and a facet 20fb having a plane orientation different from that of the facet 20fa are generated on the crystal growth surface 20g of the GaN single crystal 20 grown thereon. Here, the impurity concentration taken in facet 20fa whose plane orientation is (0001) or (000-1) is significantly different from the impurity concentration taken in facet 20fb whose plane orientation is other than (0001) and (000-1). . Therefore, in the GaN single crystal 20 grown on the main surface 10pm of the GaN seed crystal substrate 10p having a small inclination with respect to the (0001) plane or the (000-1) plane 1c in the plane orientation of the main surface 10pm, the GaN seed crystal substrate The variation in carrier concentration in the plane parallel to the main surface 10pm of 10p increases.

  Further, when the inclination with respect to the (0001) plane or the (000-1) plane 1c in the plane orientation of the main surface 10pm of the GaN seed crystal substrate 10p increases and approaches a right angle, for example, when the inclination angle α is greater than 85 °, On the crystal growth surface 20g of the GaN single crystal 20 grown on the main surface 10pm, the generation of the facet 20fb whose plane orientation is perpendicular to (0001) becomes dominant, and the GaN single crystal 20 that grows partially partially. Crystallization causes cracks in the GaN single crystal 20.

  From the above viewpoint, in order to manufacture the GaN single crystal substrate 20p having a substantially uniform carrier concentration distribution on the main surface 20pm, the plane orientation of the main surface 10pm of the GaN seed crystal substrate 10p is (0001) plane or ( 000-1) The inclination angle α with respect to the surface 1c needs to be 65 ° or more and 85 ° or less, preferably 70 ° or more and 80 ° or less, and more preferably 72 ° or more and 78 ° or less. .

  Next, referring to FIGS. 2C and 2D, in the step of cutting the GaN single crystal 20 along planes 20u and 20v parallel to the main surface of the GaN seed crystal substrate 10p to form the GaN single crystal substrate 20p. The method for cutting the GaN single crystal substrate 20p from the GaN single crystal 20 is not particularly limited, and various methods such as a wire saw, an inner peripheral blade, an outer peripheral blade, or a laser can be used. Here, the surface from which the GaN single crystal substrate 20p is cut may be shifted from being parallel to the main surface of the GaN seed crystal substrate 10p in accordance with the purpose.

  From the viewpoint of growing a highly crystalline GaN-based semiconductor layer, the average roughness Ra of the main surface 20pm of the GaN single crystal substrate 20p is preferably 50 nm or less, and more preferably 5 nm or less. The definition and measurement method of the average roughness Ra of the surface are the same as described above. In order to set the average roughness Ra of the main surface 20pm of the GaN single crystal substrate 20p to preferably 50 nm or less, more preferably 5 nm or less, the cut GaN single crystal substrate 20p is ground on its main surface 20pm and side surfaces. And / or is preferably polished. Polishing includes mechanical polishing, CMP (chemical mechanical polishing), and the like.

By the above process, the area of the main surface 20pm is 10 cm ² or more, and the surface orientation of the main surface 20pm is inclined at 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane 20c. A GaN single crystal in which the carrier concentration distribution in the main surface 20pm is substantially uniform (for example, the carrier concentration variation in the main surface 20pm is within ± 50% of the average carrier concentration in the main surface 20pm). A substrate 20p is obtained.

(Example II of Embodiment 2)
Referring to FIG. 3, another example (hereinafter referred to as Example II) of the method for manufacturing a GaN single crystal substrate of the present embodiment is as follows.

Referring to FIG. 3A, in Example II, the GaN single crystal substrate manufactured in Example I is prepared in the step of preparing GaN seed crystal substrate 10p. That is, the GaN single crystal substrate manufactured in Example I is used as the GaN seed crystal substrate 10p. The GaN single crystal substrate manufactured in Example I above has an area of the main surface of 10 cm ² or more, and the surface orientation of the main surface is 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane. In addition, the carrier concentration distribution in the main surface is substantially uniform (for example, the carrier concentration variation in the main surface is within ± 50% of the average carrier concentration in the main surface). Therefore, the GaN single crystal substrate of Embodiment 1 can be manufactured.

  Next, referring to FIG. 3B, the step of growing the GaN single crystal 20 on the main surface 10pm of the GaN seed crystal substrate 10p is performed by using a single GaN seed crystal substrate 10p instead of a plurality of GaN mother crystal pieces. Same as Example I above except that it is made of a GaN single crystal substrate.

  Next, referring to FIGS. 3B and 3C, the step of cutting the GaN single crystal 20 along a plane parallel to the main surface 10pm of the GaN seed crystal substrate 10p to form the GaN single crystal substrate 20p is as described above. This is similar to Example I. Here, the surface from which the GaN single crystal substrate 20p is cut may be shifted from being parallel to the main surface of the GaN seed crystal substrate 10p in accordance with the purpose.

By the above process, the area of the main surface 20pm is 10 cm ² or more, and the surface orientation of the main surface 20pm is inclined at 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane 20c. A GaN single crystal in which the carrier concentration distribution in the main surface 20pm is substantially uniform (for example, the carrier concentration variation in the main surface 20pm is within ± 50% of the average carrier concentration in the main surface 20pm). A substrate 20p is obtained.

Further, the thick GaN mother crystal has a principal surface with a plane orientation of 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane 1c, and the area of the principal surface is 10 cm ² or more. As long as a substrate having a large diameter can be cut, the substrate may be a GaN seed crystal substrate. However, since it is very difficult and time-consuming to produce a large-diameter GaN seed crystal substrate by this method, a plurality of GaN mother crystal pieces are formed from one GaN mother crystal as in Example 1 of Embodiment 2 above. It is important to form a GaN seed crystal substrate by cutting out and arranging such a plurality of GaN mother crystal pieces.

[GaN-based semiconductor devices]
(Embodiment 3)
Referring to FIG. 5, a GaN-based semiconductor device 100 according to an embodiment of the present invention includes at least one GaN single crystal substrate 20p according to the first embodiment and a main surface 20pm of the GaN single crystal substrate 20p. GaN-based semiconductor layer 130 as a layer.

In the GaN-based semiconductor device 100 of this embodiment, the GaN single crystal substrate 20p has an area of the main surface 20pm of 10 cm ² or more, and the surface orientation of the main surface 20pm is the (0001) plane or the (000-1) plane 20c. However, the carrier concentration distribution in the main surface 20pm is substantially uniform (for example, the carrier concentration variation in the main surface 20pm is an average carrier concentration in the main surface 20pm). Within ± 50%). For this reason, the GaN-based semiconductor device of the present embodiment has a substantially uniform distribution of device characteristics in the main surface and high device characteristics. For example, in the device of this embodiment, when an electrode is formed on a GaN single crystal substrate 20p having a substantially uniform carrier concentration distribution within the main surface 20pm, the contact resistance distribution between the single crystal substrate and the electrode is substantially equal. Uniform.

Referring to FIG. 5, the GaN-based semiconductor device 100 of this embodiment specifically includes at least one GaN-based layer on one main surface 20pm of a GaN single crystal substrate 20p having a diameter of 50 mm and a thickness of 500 μm. The semiconductor layer 130 has a multiple quantum well structure composed of an n-type GaN layer 131 having a thickness of 2 μm doped with Si, six pairs of In _0.01 Ga _0.99 N barrier layers, and an In _0.1 Ga _0.9 N well layer. A light emitting layer 132 having a thickness of 100 nm, a p-type Al _0.18 Ga _0.82 N layer 133 having a thickness of 20 nm doped with Mg, and a p-type GaN layer 134 having a thickness of 50 nm doped with Mg are sequentially stacked. Further, a Ni / Au electrode of 0.2 mm × 0.2 mm × thickness 0.5 μm, which is a p-side electrode 141, is formed on a part of the p-type GaN layer 134. A Ti / Al electrode having a thickness of 1 μm, which is an n-side electrode 142, is formed on the other main surface 20pn of the GaN single crystal substrate 20p.

[Method of manufacturing GaN-based semiconductor device]
(Embodiment 4)
Referring to FIG. 5, the manufacturing method of GaN-based semiconductor device 100 according to one embodiment of the present invention includes a step of preparing GaN single crystal substrate 20p of Embodiment 1, and a main surface 20pm of GaN single crystal substrate 20p. And a step of growing at least one GaN-based semiconductor layer 130.

In the manufacturing method of the GaN-based semiconductor device 100 of this embodiment, the area of the main surface 20pm is 10 cm ² or more, and the surface orientation of the main surface 20pm is 65 with respect to the (0001) plane or the (000-1) plane 20c. It is inclined at an angle of not less than 85 ° and not more than 85 °, and the carrier concentration distribution in the main surface 20pm is substantially uniform (for example, the variation in carrier concentration in the main surface 20pm is relative to the average carrier concentration in the main surface 20pm). At least one GaN-based semiconductor layer 130 is epitaxially grown on the GaN single crystal substrate 20p (within ± 50%). For this reason, the method for manufacturing a GaN-based semiconductor device according to this embodiment provides a GaN-based semiconductor device having a substantially uniform distribution of device characteristics in the main surface and high device characteristics. For example, in the device of this embodiment, when an electrode is formed on a GaN single crystal substrate 20p having a substantially uniform carrier concentration distribution within the main surface 20pm, the contact resistance distribution between the single crystal substrate and the electrode is substantially equal. Uniform.

  The GaN single crystal substrate 20p of the first embodiment, that is, the plane orientation of the main surface 20pm is inclined at 65 ° or more and 85 ° or less with respect to the (0001) plane or the (000-1) plane 20c, and within the main surface 20pm. GaN single crystal substrate 20p having a substantially uniform carrier concentration distribution (for example, carrier concentration variation within main surface 20pm is within ± 50% of the average carrier concentration within main surface 20pm) is prepared. The process is performed by, for example, the method for manufacturing the GaN single crystal substrate 20p of the second embodiment.

  The method for growing at least one GaN-based semiconductor layer 130 on the main surface 20pm of the GaN single crystal substrate 20p is not particularly limited, but from the viewpoint of epitaxially growing the highly crystalline GaN-based semiconductor layer 130, the HVPE method, MOCVD method, MBE method, etc. are preferably used. From the viewpoint of high productivity and reliability, the MOCVD method is more preferably used.

Referring to FIG. 5, the step of forming at least one GaN-based semiconductor layer 130 on GaN single crystal substrate 20p includes, for example, one main surface 20pm of GaN single crystal substrate 20p having a diameter of 50 mm and a thickness of 0.4 mm. Further, by MOCVD, as an at least one GaN-based semiconductor layer 130, a Si-doped n-type GaN layer 131 having a thickness of 2 μm, six pairs of an In _0.01 Ga _0.99 N barrier layer and an In _0.1 Ga _0.9 N well 100 nm thick light emitting layer 132 having a multiple quantum well structure composed of layers, Mg doped p-type Al _0.18 Ga _0.82 N layer 133 and Mg doped p-type 50 nm thick A GaN layer 134 is grown in order.

  Further, a Ni / Au electrode having a thickness of 0.5 μm, which is the p-side electrode 141, is formed on a part of the p-type GaN layer 134 by vacuum evaporation. On the other main surface 20pn of the GaN single crystal substrate 20p, a Ti / Al electrode having a thickness of 1 μm as the n-side electrode 142 is formed by vacuum deposition.

  Next, a wafer having at least one GaN-based semiconductor layer 130 formed on the GaN single crystal substrate 20p is divided into chips having a predetermined size, whereby a light emitting device having a predetermined size is obtained.

[Preparation of GaN mother crystal]
The GaN mother crystal was produced as follows. A plurality of openings having a diameter of 2 μm are planarly formed at a pitch of 4 μm on the main surface of the (111) A surface of a GaAs substrate (underlying substrate) having a diameter of 50 mm and a thickness of 0.8 mm by photolithography and etching. A 100 nm thick SiO layer (mask layer) arranged in a hexagonal close-packed manner was formed. Next, a GaN low temperature layer having a thickness of 80 nm is grown at 500 ° C. on a main surface on which a SiO layer having a plurality of openings is formed on a GaAs substrate, and then a thickness of 60 μm at 950 ° C. After growing the GaN intermediate layer, a GaN mother crystal having a thickness of 5 mm was grown at 1050 ° C. Next, the GaAs substrate was removed from the GaN mother crystal by etching using aqua regia to obtain a GaN mother crystal having a diameter of 50 mm and a thickness of 3 mm.

Example 1
1. Preparation of GaN seed crystal substrate Referring to FIG. 2 (A), both main surfaces of (0001) surface and (000-1) surface 1c, which are both main surfaces of GaN mother crystal 1, are ground and polished. The average roughness Ra was 5 nm. Here, the average roughness Ra of the surface was measured by AFM.

  Next, referring to FIG. 2A, a GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is parallel to the {20-21} plane (perpendicular to the <20-21> direction). A plurality of GaN mother crystal pieces 1p having a {20-21} main surface were cut out. Subsequently, four surfaces of each cut GaN mother crystal piece 1p that were not ground and polished were ground and polished, and the average roughness Ra of these four surfaces was set to 5 nm. Thus, a plurality of GaN mother crystal pieces 1p having an average roughness Ra of the main surface of {20-21} of 5 nm were obtained. Among the GaN mother crystal pieces 1p, there was a crystal piece whose plane orientation of the main surface did not completely match {20-21}. The surface orientation was within ± 0.1 ° with respect to {20-21}. Here, the inclination angle was measured by an X-ray diffraction method.

  Next, referring to FIG. 2B, the {20-21} main surfaces 10pm of the plurality of GaN mother crystal pieces 1p are parallel to each other, and [0001] of those GaN mother crystal pieces 1p The GaN seed crystal substrate 10p having a diameter of 50 mm was prepared by arranging the GaN mother crystal pieces 1p adjacent to each other in the lateral direction so that the directions are the same, and further removing a part of the outer peripheral portion. .

2. Growth of GaN Single Crystal Next, referring to FIG. 2 (C), 10 volume% hydrogen chloride gas and 90 volume% nitrogen gas are applied to the {20-21} main surface 10pm of the GaN seed crystal substrate 10p. After being treated at 800 ° C. for 2 hours in a mixed gas atmosphere, a GaN single crystal 20 was grown on the main surface 10 pm by HVPE method at a crystal growth temperature of 1050 ° C. at a growth rate of 80 μm / hr for 50 hours. .

3. Formation of GaN Single Crystal Substrate Next, referring to FIG. 2D, the GaN single crystal 20 is sliced by planes 20u and 20v parallel to the main surface 10pm of {20-21} of the GaN seed crystal substrate 10p. As a result, a GaN single crystal substrate 20p having a surface orientation of the main surface 20pm of {20-21}, a diameter of 50 mm, and a thickness of 0.5 mm was obtained. In the GaN single crystal substrate 20p, the main surface 20pm was further ground and polished so that the average roughness Ra of the main surface 20pm was 5 nm. Referring to FIG. 4A, {20-21} main surface 20pm of GaN single crystal substrate 20p has an inclination angle α of 75 ° with respect to (0001) surface 20c.

The carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above is set to a pitch of 2 mm in each of two directions orthogonal to each other from the center toward the outer periphery in the main surface 20pm by the van der Pauw method. Measurement was performed at 400 measurement points excluding the measurement points on the outer periphery from the measurement points. The average carrier concentration was 5.7 × 10 ¹⁷ cm ⁻³ , the lowest carrier concentration was 3.9 × 10 ¹⁷ cm ⁻³ , and the highest carrier concentration was 7.2 × 10 ¹⁷ cm ⁻³ . Therefore, the variation of the carrier concentration with respect to the average carrier concentration in the main surface was as small as −31.6% to + 26.3%.

  In addition, the specific resistance in the main surface 20pm of the GaN single crystal substrate 20p is measured from the measurement point with a pitch of 2 mm in each of two directions orthogonal to each other from the center to the outer periphery in the main surface 20pm by the van der Pauw method. Measurement was performed at 400 measurement points excluding the measurement points. The average specific resistance was 0.019 Ω · cm, the minimum specific resistance was 0.014 Ω · cm, and the maximum specific resistance was 0.026 Ω · cm. Therefore, the variation of the specific resistance with respect to the average specific resistance in the main surface was as small as −26% to + 37%.

4). Production of GaN-based semiconductor device Next, on one main surface 20pm of the GaN single crystal substrate 20p (diameter 50 mm × thickness 0.4 mm), at least one GaN-based semiconductor layer 130 is formed by MOCVD. Si-doped n-type GaN layer 131 having a thickness of 2 μm (average carrier concentration: 2 × 10 ¹⁸ cm ⁻³ ), 6 pairs of In _0.01 Ga _0.99 N barrier layers and In _0.1 Ga _0.9 N well layers Light emitting layer 132 having a multiple quantum well structure with a thickness of 100 nm, p-type Al _0.18 Ga _0.82 N layer 133 with a thickness of 20 nm doped with Mg (average carrier concentration: 3 × 10 ¹⁷ cm ⁻³ ) and Mg are doped A p-type GaN layer 134 (average carrier concentration: 1 × 10 ¹⁸ cm ⁻³ ) having a thickness of 50 nm was grown in order.

  Next, a 0.2 mm × 0.2 mm × 0.5 μm thick Ni / Au electrode is formed as the p-side electrode 141 at a pitch of 1 mm in two directions orthogonal to each other on the p-type GaN layer 134 by vacuum deposition. Formed. Further, a Ti / Al electrode having a thickness of 1 μm was formed as the n-side electrode 142 on the other main surface 20pn of the GaN single crystal substrate 20p by a vacuum deposition method.

  Next, a wafer on which the at least one GaN-based semiconductor layer 130 is formed on the GaN single crystal substrate 20p so that each p-side electrode is positioned at the center of each chip is formed on the GaN single crystal substrate 20p. The wafer was divided (chip-formed) into a plurality of 1 mm × 1 mm chips, that is, GaN-based semiconductor devices, except for the outer peripheral portion of the wafer where the carrier concentration and specific resistance distribution in the main surface 20 pm were not measured. The GaN-based semiconductor device 100 thus obtained was an LED (light emitting diode) having an emission peak wavelength of 450 nm.

  The luminance on the main surface of the LED (GaN-based semiconductor device 100) manufactured as described above was measured for the above-mentioned 1600 LED chips using a luminance measurement integrating sphere. The average luminance obtained with the LED of Example 1 was defined as the average relative luminance 1.0, and the average relative luminance and the sample variance of the relative luminance of each example were expressed. The average relative luminance was as large as 1.0, and the sample variance of the relative luminance was as small as 0.12. The results are summarized in Table 1.

(Example 2)
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is formed in a plane parallel to the {20-2-1} plane (perpendicular to the <20-2-1> direction). A plurality of GaN mother crystal pieces 1p having a {20-2-1} main surface, and grinding and polishing the main surfaces to average roughness of the main surfaces. A GaN single crystal substrate 20p having a principal surface 20pm of {20-2-1} was formed in the same manner as in Example 1 except that the GaN mother crystal piece 1p with Ra of 5 nm was used. Referring to FIG. 4B, the {20-2-1} main surface 20pm of the GaN single crystal substrate 20p has an inclination angle α of 75 ° with respect to the (000-1) plane 20c.

Regarding the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above, the average carrier concentration is 7.1 × 10 ¹⁷ cm ⁻³ and the minimum carrier concentration is 5.0 × 10 ¹⁷ cm ^−3. The maximum carrier concentration was 8.2 × 10 ¹⁷ cm ⁻³ . Therefore, the variation in carrier concentration with respect to the average carrier concentration in the main surface was as small as −29.6% to + 15.5%. Further, regarding the specific resistance in the main surface 20pm of the GaN single crystal substrate 20p, the average specific resistance was 0.016 Ω · cm, the minimum specific resistance was 0.012 Ω · cm, and the maximum specific resistance was 0.020 Ω · cm. Therefore, the variation in specific resistance with respect to the average specific resistance in the main surface was as small as −25% to + 25%.

  Further, using this GaN single crystal substrate 20p, an LED which is a GaN-based semiconductor device was manufactured in the same manner as in Example 1. Regarding the luminance on the main surface of the manufactured LED (GaN-based semiconductor device 100), the average relative luminance was as large as 1.2, and the sample variance of the relative luminance was as small as 0.11. The results are summarized in Table 1.

(Example 3)
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is a plane parallel to the {22-42} plane (a plane perpendicular to the <22-42> direction). By slicing, a plurality of GaN mother crystal pieces 1p having a {22-42} main surface are cut out, and the main surfaces are ground and polished so that the average roughness Ra of the main surfaces is 5 nm. A GaN single crystal substrate 20p having a principal plane 20pm of {22-42} was formed in the same manner as in Example 1 except that the mother crystal piece 1p was used. Referring to FIG. 4C, the {22-42} main surface 20pm of the GaN single crystal substrate 20p has an inclination angle α of 73 ° with respect to the (0001) plane 20c.

Regarding the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above, the average carrier concentration is 6.1 × 10 ¹⁷ cm ⁻³ and the minimum carrier concentration is 3.5 × 10 ¹⁷ cm ^−3. The highest carrier concentration was 8.7 × 10 ¹⁷ cm ⁻³ . Therefore, the carrier concentration variation with respect to the average carrier concentration in the main surface was as small as −42.6% to + 42.6%. Further, regarding the specific resistance in the main surface 20pm of the GaN single crystal substrate 20p, the average specific resistance was 0.020 Ω · cm, the minimum specific resistance was 0.012 Ω · cm, and the maximum specific resistance was 0.029 Ω · cm. Therefore, the variation in specific resistance with respect to the average specific resistance in the main surface was as small as −40% to + 45%.

  Further, using this GaN single crystal substrate 20p, an LED which is a GaN-based semiconductor device was manufactured in the same manner as in Example 1. Regarding the luminance on the main surface of the manufactured LED (GaN-based semiconductor device 100), the average relative luminance was as large as 0.9, and the sample variance of the relative luminance was as small as 0.14. The results are summarized in Table 1.

Example 4
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is formed on a plane parallel to the {22-4-2} plane (perpendicular to the <22-4-2> direction). A plurality of GaN mother crystal pieces 1p having {22-4-2} main surfaces, and grinding and polishing the main surfaces to average roughness of the main surfaces. A GaN single crystal substrate 20p having a principal plane 20pm of {22-4-2} was formed in the same manner as in Example 1 except that the GaN mother crystal piece 1p with Ra of 5 nm was used. Referring to FIG. 4D, the {22-4-2} main surface 20pm of the GaN single crystal substrate 20p has an inclination angle α of 73 ° with respect to the (000-1) plane 20c.

Regarding the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above, the average carrier concentration is 8.5 × 10 ¹⁷ cm ⁻³ and the minimum carrier concentration is 5.0 × 10 ¹⁷ cm ^−3. The highest carrier concentration was 12.5 × 10 ¹⁷ cm ⁻³ . Therefore, the variation of the carrier concentration with respect to the average carrier concentration in the main surface was as small as −41.2% to + 47.1%. Further, regarding the specific resistance within the main surface 20pm of the GaN single crystal substrate 20p, the average specific resistance was 0.015 Ω · cm, the minimum specific resistance was 0.008 Ω · cm, and the maximum specific resistance was 0.020 Ω · cm. Therefore, the variation in specific resistance with respect to the average specific resistance in the main surface was as small as −47% to + 33%.

  Further, using this GaN single crystal substrate 20p, an LED which is a GaN-based semiconductor device was manufactured in the same manner as in Example 1. Regarding the luminance on the main surface of the manufactured LED (GaN-based semiconductor device 100), the average relative luminance was as large as 0.86, and the sample variance of the relative luminance was as small as 0.14. The results are summarized in Table 1.

(Comparative Example 1)
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is a plane parallel to the {10-10} plane (a plane perpendicular to the <10-10> direction). By slicing, GaN mother crystal pieces 1p having {10-10} main surfaces are cut out, and the main surfaces are ground and polished to obtain an average roughness Ra of the main surfaces of 5 nm. A GaN single crystal 20 was grown in the same manner as in Example 1 except that the mother crystal piece 1p was used. The GaN single crystal 20 was partially polycrystallized and cracked starting from the polycrystallized portion. Therefore, a GaN single crystal substrate could not be obtained, and a GaN-based semiconductor device could not be manufactured. The results are summarized in Table 1.

(Comparative Example 2)
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is a plane parallel to the {11-20} plane (a plane perpendicular to the <11-20> direction). By slicing, a plurality of GaN mother crystal pieces 1p having a {11-20} main surface are cut out, and the main surfaces are ground and polished so that the average roughness Ra of the main surfaces is 5 nm. A GaN single crystal 20 was grown in the same manner as in Example 1 except that the mother crystal piece 1p was used. The GaN single crystal 20 was partially polycrystallized and cracked starting from the polycrystallized portion. Therefore, a GaN single crystal substrate could not be obtained, and a GaN-based semiconductor device could not be manufactured. The results are summarized in Table 1.

(Comparative Example 3)
In preparation of the GaN seed crystal substrate 10p, a GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is a plane parallel to the {10-11} plane (a plane perpendicular to the <10-11> direction). By slicing, GaN mother crystal pieces 1p having a {10-11} main surface are cut out, and the main surfaces are ground and polished so that the average roughness Ra of the main surfaces is 5 nm. A GaN single crystal substrate 20p having a principal plane 20pm of {10-11} was formed in the same manner as in Example 1 except that the mother crystal piece 1p was used. The {10-11} main surface of the GaN single crystal substrate 20p has an inclination angle α of 62 ° with respect to the (0001) plane.

Regarding the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above, the average carrier concentration is 4.5 × 10 ¹⁷ cm ⁻³ and the minimum carrier concentration is 3.5 × 10 ¹⁶ cm ^−3. The highest carrier concentration was 7.1 × 10 ¹⁷ cm ⁻³ . Therefore, the variation of the carrier concentration with respect to the average carrier concentration in the main surface was as large as -92.2% to + 57.8%. Further, regarding the specific resistance within the main surface 20pm of the GaN single crystal substrate 20p, the average specific resistance was 0.073 Ω · cm, the minimum specific resistance was 0.014 Ω · cm, and the maximum specific resistance was 0.29 Ω · cm. Therefore, the variation of the specific resistance with respect to the average specific resistance in the main surface was as large as -81% to + 297%.

  Further, using this GaN single crystal substrate 20p, an LED which is a GaN-based semiconductor device was manufactured in the same manner as in Example 1. Regarding the luminance on the main surface of the manufactured LED (GaN-based semiconductor device 100), the average relative luminance was as small as 0.55, and the sample variance of the relative luminance was as large as 0.35. The results are summarized in Table 1.

(Comparative Example 4)
In the preparation of the GaN seed crystal substrate 10p, the GaN mother crystal 1 having an average roughness Ra of both main surfaces of 5 nm is a plane parallel to the {11-22} plane (a plane perpendicular to the <11-22> direction). By slicing, a plurality of GaN mother crystal pieces 1p having a {11-22} main surface are cut out, and the main surfaces are ground and polished so that the average roughness Ra of the main surfaces is 5 nm. A GaN single crystal substrate 20p having a principal plane 20pm of {11-22} was formed in the same manner as in Example 1 except that the mother crystal piece 1p was used. The {11-22} main surface of the GaN single crystal substrate 20p has an inclination angle α of 58 ° with respect to the (0001) plane.

Regarding the carrier concentration in the main surface 20pm of the GaN single crystal substrate 20p formed as described above, the average carrier concentration is 4.9 × 10 ¹⁷ cm ⁻³ and the minimum carrier concentration is 3.1 × 10 ¹⁶ cm ^−3. The highest carrier concentration was 6.8 × 10 ¹⁷ cm ⁻³ . Therefore, the variation of the carrier concentration with respect to the average carrier concentration in the main surface was as large as -93.7% to + 38.8%. Further, regarding the specific resistance within the main surface 20pm of the GaN single crystal substrate 20p, the average specific resistance was 0.11 Ω · cm, the minimum specific resistance was 0.015 Ω · cm, and the maximum specific resistance was 0.32 Ω · cm. Therefore, the variation of the specific resistance with respect to the average specific resistance in the main surface was as large as -86% to + 190%.

  Further, using this GaN single crystal substrate 20p, an LED which is a GaN-based semiconductor device was manufactured in the same manner as in Example 1. Regarding the luminance on the main surface of the manufactured LED (GaN-based semiconductor device 100), the average relative luminance was as small as 0.41, and the sample variance of the relative luminance was as large as 0.31. The results are summarized in Table 1.

  As is apparent from Table 1, the plane orientation of the main surface is inclined at 65 ° to 85 ° with respect to the (0001) plane or (000-1) plane, and the carrier concentration distribution in the main plane is substantially Use of a GaN single crystal substrate that is uniformly uniform (within ± 50% of carrier concentration variation with respect to the average carrier concentration in the main surface), the average light emission intensity on the main surface is large and the light emission intensity distribution is substantially uniform. A GaN-based semiconductor device was obtained (the sample dispersion of the relative luminance with respect to the average relative luminance in the main surface was 0.2 or less and the variation in the emission intensity with respect to the average emission intensity was small).

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 GaN mother crystal, 1c, 20c (0001) plane or (000-1) plane, 1p GaN mother crystal piece, 1 pm, 10 pm, 20 pm, 20 pn main surface, 10 p GaN seed crystal substrate, 20 GaN single crystal, 20 fa, 20 fb Facet, 20g crystal growth surface, 20p GaN single crystal substrate, 20u, 20v parallel plane, 100 GaN semiconductor device, 130 GaN semiconductor layer, 131 n-type GaN layer, 132 light emitting layer, 133 p-type Al _0.18 Ga _0.82 N Layer, 134 p-type GaN layer, 141 p-side electrode, 142 n-side electrode.

Claims (6)

The area of the main surface is 10 cm ² or more,
The plane orientation of the main surface is inclined at 72 ° or more and 78 ° or less with respect to the (0001) plane or the (000-1) plane,
The GaN single crystal substrate, wherein the carrier concentration variation in the main surface is within ± 50% with respect to the average carrier concentration in the main surface.   2. The GaN single crystal substrate according to claim 1, wherein variation in specific resistance within the main surface is within ± 50% with respect to an average specific resistance within the main surface.   The GaN single crystal substrate according to claim 2, wherein an average specific resistance in the main surface is 0.1 Ωcm or less. A method for producing a GaN single crystal substrate according to claim 1,
Preparing a GaN seed crystal substrate having a principal surface area of 10 cm ² or more and an orientation of the principal surface that is inclined at 72 ° or more and 78 ° or less with respect to the (0001) plane or the (000-1) plane. When,
Growing a GaN single crystal on the main surface of the GaN seed crystal substrate;
Cutting the GaN single crystal along a plane parallel to the main surface of the GaN seed crystal substrate to form the GaN single crystal substrate.   A GaN-based semiconductor device comprising the GaN single-crystal substrate of claim 1 and at least one GaN-based semiconductor layer formed on the main surface of the GaN single-crystal substrate. Preparing the GaN single crystal substrate of claim 1;
And a step of growing at least one GaN-based semiconductor layer on the main surface of the GaN single crystal substrate.

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