GaN single crystal substrate and method of manufacturing thereof and GaN-based semiconductor device and method of manufacturing thereof
A GaN single crystal substrate has a main surface with an area of not less than 10 cm 2 , the main surface has a plane orientation inclined by not less than 65° and not more than 85° with respect to one of a (0001) plane and a (000-1) plane, and the substrate has at least one of a substantially uniform distribution of a carrier concentration in the main surface, a substantially uniform distribution of a dislocation density in the main surface, and a photoelasticity distortion value of not more than 5×10 −5 , the photoelasticity distortion value being measured by photoelasticity at an arbitrary point in the main surface when light is applied perpendicularly to the main surface at an ambient temperature of 25° C. Thus, the GaN single crystal substrate suitable for manufacture of a GaN-based semiconductor device having a small variation of characteristics can be obtained.
1. A GaN single crystal substrate having a main surface with an area of not less than 10 cm 2 , said main surface having a plane orientation inclined by not less than 65° and not more than 85° with respect to one of a (0001) plane and a (000-1) plane, and said substrate having at least one of a substantially uniform distribution of a carrier concentration in said main surface, a substantially uniform distribution of a dislocation density in said main surface, and a photoelasticity distortion value of not more than 5×10 −5 , the photoelasticity distortion value being measured by photoelasticity at an arbitrary point in said main surface when light is applied perpendicularly to said main surface at an ambient temperature of 25° C.
2. The GaN single crystal substrate according to claim 1 , wherein a variation of the carrier concentration in said main surface is within ±50% with respect to an average carrier concentration in said main surface.
3. The GaN single crystal substrate according to claim 1 , wherein a distribution of a specific resistance in said main surface is substantially uniform.
4. The GaN single crystal substrate according to claim 3 , wherein a variation of the specific resistance in said main surface is within ±50% with respect to an average specific resistance in said main surface.
5. The GaN single crystal substrate according to claim 3 , wherein an average specific resistance in said main surface is not more than 0.1 Ωcm.
6. The GaN single crystal substrate according to claim 1 , wherein a variation of the dislocation density in said main surface is within ±100% with respect to an average dislocation density in said main surface.
7. The GaN single crystal substrate according to claim 1 , wherein the dislocation density in said main surface is not more than 5×10 6 cm −2 .
8. The GaN single crystal substrate according to claim 1 , wherein a variation of said photoelasticity distortion value in said main surface is within ±100% with respect to an average value of said photoelasticity distortion value in said main surface.
9. The GaN single crystal substrate according to claim 1 , wherein the plane orientation of said main surface is inclined in <10-10> direction with respect to one of the (0001) plane and the (000-1) plane.
10. The GaN single crystal substrate according to claim 1 , wherein a half width of an x-ray diffraction peak obtained by x-ray diffraction rocking curve measurement for one of a combination of a (0002) plane and a (20-20) plane, and a combination of a (0002) plane and a (22-40) plane is not more than 300 arc sec in a whole of said main surface.
11. A method of manufacturing a GaN single crystal substrate as recited in claim 1 , comprising the steps of: preparing a GaN seed crystal substrate having a main surface with an area of not less than 10 cm 2 , said main surface having a plane orientation inclined by not less than 65° and not more than 85° with respect to one of a (0001) plane and a (000-1) plane; growing a GaN single crystal on said main surface of said GaN seed crystal substrate; and forming said GaN single crystal substrate by cutting said GaN single crystal along a plane that is parallel with said main surface of said GaN seed crystal substrate.
12. A GaN-based semiconductor device comprising a GaN single crystal substrate as recited in claim 1 , and at least one GaN-based semiconductor layer formed on said main surface of said GaN single crystal substrate.
13. A method of manufacturing a GaN-based semiconductor device comprising the steps of: preparing a GaN single crystal substrate as recited in claim 1 ; and growing at least one GaN-based semiconductor layer on said main surface of said GaN single crystal substrate.
14. The GaN single crystal substrate according to claim 1 , wherein the plane orientation is inclined by not less than 70° and not more than 80°.
15. The GaN single crystal substrate according to claim 1 , wherein the plane orientation is inclined by not less than 72° and not more than 78°.