Nitride-based semiconductor device and method of manufacturing the same

1. A nitride-based semiconductor device comprising:

a substrate;

a first step portion formed on a main surface side of a first side end surface of said substrate;

a second step portion formed on said main surface side of a second side end surface substantially parallel to said first side end surface on an opposite side of said first side end surface; and

a nitride-based semiconductor layer whose first side surface is a (000-1) plane starting from a first side wall of said first step portion and a second side surface starting from a second side wall of said second step portion on said main surface;

wherein,

said substrate includes a base substrate and an underlayer formed on said base substrate,

said underlayer has a first crack and a second crack,

a first inner side surface of said first crack is said first side wall and a second inner side surface of said second crack is said second side wall,

said first side surface is formed starting from said first inner side surface and said second side surface is formed starting from said second inner side surface,

said first crack and said second crack extend to the direction parallel to a (0001) plane of said underlayer and said main surface.

2. The nitride-based semiconductor device according to claim 1 , wherein

said nitride-based semiconductor layer has an emission layer, and

said nitride-based semiconductor device is a light-emitting device.

3. The nitride-based semiconductor device according to claim 1 , wherein

said first side wall is formed by a (000-1) plane.

4. The nitride-based semiconductor device according to claim 1 , wherein

said second side surface is formed by a {A+B, A, −2A−B, 2A+B} plane (A and B satisfy A≧0 and B≧0, and at least either one of A and B is a nonzero integer).

5. The nitride-based semiconductor device according to claim 4 , wherein

said second side surface is formed by a (1-101) plane or a (11-22) plane.

6. The nitride-based semiconductor device according to claim 1 , wherein

said nitride-based semiconductor layer is so formed that a plane area of said nitride-based semiconductor layer is reduced in a direction away from said substrate along a direction of stacking of said nitride-based semiconductor layer by said first side surface and said second side surface.

7. The nitride-based semiconductor device according to claim 1 , wherein

at least either said first side surface or said second side surface is formed at slant so as to form an obtuse angle with respect to said main surface.

8. The nitride-based semiconductor device according to claim 1 , wherein

said first side surface and said second side surface are formed by crystal growth facets of said nitride-based semiconductor layer.

9. The nitride-based semiconductor device according to claim 1 , wherein said underlayer is made of AlGaN.

10. The nitride-based semiconductor device according to claim 1 , wherein

when lattice constants of said base substrate and said underlayer are c1 and c2 respectively, c1 and c2 satisfy the relation of c1>c2.

11. A nitride-based semiconductor device comprising:

a substrate;

a first step portion formed on a main surface side of a first side end surface of said substrate;

a second step portion formed on said main surface side of a second side end surface substantially parallel to said first side end surface on an opposite side of said first side end surface; and

a nitride-based semiconductor layer whose first side surface is a (000-1) plane starting from a first side wall of said first step portion and a second side surface starting from a second side wall of said second step portion on said main surface, wherein

said substrate includes a base substrate and an underlayer made of AlGaN formed on said base substrate,

when lattice constants of said base substrate and said underlayer are c 1 and c 2 respectively, c 1 and c 2 satisfy the relation of c1>c2, and

said underlayer has a first crack and a second crack,

a first inner side surface of said first crack is said first side wall and a second inner side surface of said second crack is said second side wall,

said first side surface is formed starting from said first inner side surface and said second side surface is formed starting from said second inner side surface,

said first crack and said second crack extend to the direction parallel to a (0001) plane of said underlayer and said main surface.

12. The nitride-based semiconductor device according to claim 1 , wherein

said first side surface and said second side surface extend along a first direction, and said nitride-based semiconductor device has an optical waveguide extending along said first direction.

13. The nitride-based semiconductor device according to claim 11 , wherein

said nitride-based semiconductor layer has an emission layer, and

said nitride-based semiconductor device is a light-emitting device.

14. The nitride-based semiconductor device according to claim 11 , wherein

said first side wall is formed by a (000-1) plane.

15. The nitride-based semiconductor device according to claim 11 , wherein

said second side surface is formed by a {A+B, A, −2A−B, 2A+B} plane (A and B satisfy A≧0 and B≧0, and at least either one of A and B is a nonzero integer).

16. The nitride-based semiconductor device according to claim 11 , wherein

said second side surface is formed by a (1-101) plane or a (11-22) plane.

17. The nitride-based semiconductor device according to claim 11 , wherein

said nitride-based semiconductor layer is so formed that a plane area of said nitride-based semiconductor layer is reduced in a direction away from said substrate along a direction of stacking of said nitride-based semiconductor layer by said first side surface and said second side surface.

18. The nitride-based semiconductor device according to claim 11 , wherein

at least either said first side surface or said second side surface is formed at slant so as to form an obtuse angle with respect to said main surface.

19. The nitride-based semiconductor device according to claim 11 , wherein

said first side surface and said second side surface are formed by crystal growth facets of said nitride-based semiconductor layer.

20. The nitride-based semiconductor device according to claim 11 , wherein

said first side surface and said second side surface extend along a first direction, and said nitride-based semiconductor device has an optical waveguide extending along said first direction.