Single-crystal substrate, group-III nitride crystal obtained using the same, and process for producing group-III nitride crystal
View Patent ↗Provided is a base substrate with which a Group-III nitride crystal having a large area and a large thickness can be grown while inhibiting crack generation. A single-crystal substrate for use in growing a Group-III nitride crystal thereon, which satisfies the following expression (1), wherein Z1 (μm) is an amount of warpage of physical shape in a growth surface of the single-crystal substrate and Z2 (μm) is an amount of warpage calculated from a radius of curvature of crystallographic-plane shape in a growth surface of the single-crystal substrate: −40<Z2/Z1<−1: Expression (1).
1. A single-crystal substrate for use in growing a Group-III nitride crystal thereon, which satisfies the following expression (1), wherein Z1 (μm) is an amount of warpage of physical shape in a growth surface of the single-crystal substrate and Z2 (μm) is an amount of warpage calculated from a radius of curvature of crystallographic-plane shape in a growth surface of the single-crystal substrate, and said growth surface has a convex shape and a back surface of said substrate has a concave shape, or said growth surface has a concave shape and a back surface of said substrate has a convex shape:
−40 <Z 2 /Z 1<−1 Expression (1).
2. The single-crystal substrate according to claim 1 , wherein the growth surface of the single-crystal substrate comprises a Group-III nitride crystal.
3. The single-crystal substrate according to claim 1 , which has an area of 20 cm 2 or more.
4. The single-crystal substrate according to claim 1 , which has a value of the Z1 of −50 μm to 50 μm.
5. The single-crystal substrate according to claim 1 , wherein the single-crystal substrate is a hexagonal crystal, and a crystallographic plane of the growth surface thereof is any one of a {0001} plane, a {10-10} plane, a {11-20} plane, a {11-22} plane, and a {20-21} plane.
6. The single-crystal substrate according to claim 1 , which has a absolute value of the Z2 of 31 μm to 312 μm.
7. The single-crystal substrate according to claim 1 , which has a value of the Z1 of −30 μm to 50 μm.
8. The single-crystal substrate according to claim 1 , which has a value of the Z1 of −50 μm to 40 μm.
9. The single-crystal substrate according to claim 1 , which has a value of the Z1 of −50 μm to 30 μm.
10. The single-crystal substrate according to claim 1 , wherein said substrate has an area of 46 cm 2 or more.
11. The single-crystal substrate according to claim 1 , wherein said substrate has an area of 81 cm 2 or more.
12. The single-crystal substrate according to claim 1 , wherein said substrate has thickness of 100 to 1,000 μm.
13. The single-crystal substrate according to claim 1 , wherein said substrate has thickness of 300 to 500 μm.
14. The single-crystal substrate according to claim 1 , wherein said Group III nitride is gallium nitride.
15. The single-crystal substrate according to claim 1 , wherein said growth surface is a polished surface.
16. A single-crystal substrate for use in growing a Group-III nitride crystal thereon, which satisfies the following expressions (2) and (3), wherein Z1(μm) is an amount of warpage of physical shape in a growth surface of the single-crystal substrate and Z2 (μm) is an amount of warpage calculated from a radius of curvature of crystallographic-plane shape in a growth surface of the single crystal substrate and a back surface of said substrate has a concave shape:
Z 1> Expression (2)
Z 2< Expression (3).
17. A process for producing a Group-III nitride crystal, the process comprising preparing the single-crystal substrate according to claim 1 and growing a Group-III nitride crystal on the single-crystal substrate.
18. The process for producing a Group-III nitride crystal according to claim 17 , wherein the Group-III nitride crystal is grown by a method which is any one of an HVPE method, a sodium flux method, and a solvothermal method.
19. The single-crystal substrate according to claim 1 , which has a value of the Z1 of −40 μm to 50 μm.