III-V nitride semiconductor substrate and its production method
A self-supported III-V nitride semiconductor substrate having a substantially uniform carrier concentration distribution in a surface layer existing from a top surface to a depth of at least 10 μm is produced by growing a III-V nitride semiconductor crystal while forming a plurality of projections on a crystal growth interface at the initial or intermediate stage of crystal growth; conducting the crystal growth until recesses between the projections are buried, so that the crystal growth interface becomes flat; and continuing the crystal growth to a thickness of 10 μm or more while keeping the crystal growth interface flat.
1. A self-supported III-V nitride semiconductor substrate having a substantially uniform carrier concentration distribution at least on its outermost surface, wherein said substrate has a carrier concentration of 1×10 17 cm −3 or more, and wherein variations in the carrier concentration are within ±25% in said outermost surface, said variations in the carrier concentration lying in a surface (in-plane) thereof.
2. The self-supported III-V nitride semiconductor substrate according to claim 1 , wherein said substantially uniform carrier concentration distribution in a surface layer exists from the top surface to a depth of at least 10 μm.
3. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein variations in the carrier concentration are not larger on a top surface of said substrate than on a bottom surface of said substrate.
4. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein a top surface of said substrate is polished.
5. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein a bottom surface of said substrate is polished.
6. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein said substrate has a thickness of 200 μm to 1 mm.
7. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein a top surface of said substrate is a (0001) group-III surface.
8. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein said substrate has a dislocation density lower on a top surface of said substrate than on a bottom surface of said substrate.
9. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein said substrate comprises a layer of GaN or AlGaN.
10. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein said III-V nitride semiconductor substrate is doped with an impurity.
11. The III-V nitride semiconductor substrate according to claim 1 or 2 , wherein at least part of said III-V nitride semiconductor substrate is grown by an HYPE method.
12. A III-V nitride semiconductor substrate having a substantially uniform carrier concentration distribution at least on its outermost surface, wherein said substrate has a carrier concentration of less than 1×10 17 cm −3 , and wherein variations in the carrier concentration are within ±100% in said outermost surface, said variations in the carrier concentration lying in a surface (in-plane) thereof.
13. The self-supported III-V nitride semiconductor substrate according to claim 12 , wherein said substantially uniform carrier concentration distribution in a surface layer exists from the top surface to a depth of at least 10 μm.
14. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein variations in the carrier concentration are not larger on a top surface of said substrate than on a bottom surface of said substrate.
15. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein a top surface of said substrate is polished.
16. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein a bottom surface of said substrate is polished.
17. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein said substrate has a thickness of 200 μm to 1 mm.
18. The III-V nitride semiconductor substrate according claim 12 or 13 , wherein a top surface of said substrate is a (0001) group-III surface.
19. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein the said substrate has a dislocation density lower on a top surface of said substrate than on a bottom surface of said substrate.
20. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein said substrate comprises a layer of GaN or AIGaN.
21. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein said III-V nitride semiconductor substrate is doped with an impurity.
22. The III-V nitride semiconductor substrate according to claim 12 or 13 , wherein at least part of said III-V nitride semiconductor substrate is grown by an HVPE method.