III-V group nitride system semiconductor substrate

1. A III-V group nitride system semiconductor substrate, comprising:

a III-V group nitride system single crystal, wherein:

the III-V group nitride system semiconductor substrate comprises: a flat surface; and

an axial orientation of the III-V group nitride system single crystal forms a convergence point inside a plane of the substrate,

such that a vector made by projecting on a surface of the substrate a normal vector of a low index surface closest to the substrate surface at an arbitrary point in a plane of the substrate is converged on a specific point or a specific region inside the plane of the substrate.

2. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the substrate comprises a self-standing substrate including the III-V group nitride system single crystal.

3. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the III-V group nitride system single crystal comprises a hexagonal system.

4. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the III-V group nitride system single crystal comprises a hexagonal system and a low index surface comprises a C-face.

5. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the III-V group nitride system single crystal comprises a hexagonal system and a low index surface comprises a III-group C-face.

6. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the III-V group nitride system single crystal comprises a hexagonal system and a low index surface comprises an A-face, M-face or R-face.

7. The III-V group nitride system semiconductor substrate according to claim 1 , wherein:

the substrate comprises a surface mirror-finished by polishing.

8. The III-V group nitride system semiconductor substrate according to claim 1 , wherein a distribution of crystal axes of the substrate forms a convergence point inside the plane of the substrate.

9. The III-V group nitride system semiconductor substrate according to claim 8 , wherein the distribution of crystal axes of the substrate forms a convergence point on a polished surface of the substrate.

10. The III-V group nitride system semiconductor substrate according to claim 1 , wherein an inclination of crystal axes of the substrate converge on one of a specific point inside the substrate and a specific region inside the substrate.

11. The III-V group nitride system semiconductor substrate according to claim 10 , wherein the inclination of crystal axes comprises a distribution of C-axis inclination direction.

12. The III-V group nitride system semiconductor substrate according to claim 11 , wherein the C-axis inclination direction is distributed toward the inside of the substrate.

13. A III-V group nitride system semiconductor substrate, comprising:

a first III-V group nitride system semiconductor substrate, comprising:

a III-V group nitride system single crystal, wherein:

the first III-V group nitride system semiconductor substrate comprises a flat surface;

an axial orientation of the III-V group nitride system single crystal forms a convergence point inside a plane of the substrates such that,

a vector made by projecting on a surface of the substrate a normal vector of a low index surface closest to the substrate surface at an arbitrary point in a plane of the substrate is converged on a specific point or a specific region inside the plane of the substrate; and

a crystal layer formed on the first III-V group nitride system semiconductor substrate, comprises a layer represented by Al x Ga 1-x N (0<x<1).

14. A III-V group nitride system semiconductor device, comprising:

a III-V group nitride system semiconductor substrate, comprising a III-V group nitride system single crystal, wherein:

the III-V group nitride system semiconductor substrate comprises a flat surface; and

an axial orientation of the III-V group nitride system single crystal forms a convergence point inside a plane of the substrate such that,

a vector made by projecting on a surface of the substrate a normal vector of a low index surface closest to the substrate surface at an arbitrary point in a plane of the substrate is converged on a specific point or a specific region inside the plane of the substrate; and

a plurality of crystal layers are formed on the III-V group nitride system semiconductor substrate, and comprise a layer represented by Al x Ga 1−x N (0<x≦1).

15. A lot of III-V group nitride system semiconductor substrate, comprising:

a plurality of III-V group nitride system semiconductor substrates, wherein:

 each of the plurality of III-V group nitride system semiconductor substrates comprises a III-V group nitride system single crystal, wherein:

the each III-V group nitride system semiconductor substrate comprises a flat surface; and

an axial orientation of the III-V group nitride system single crystal forms a convergence point inside a plane of the substrate such that,

 a vector made by projecting on a surface of the substrate a normal vector of a low index surface closest to the substrate surface at an arbitrary point in a plane of the substrate is converged on a specific point or a specific region inside the plane of the substrate.

16. A III-V group nitride system semiconductor substrate, comprising:

a III-V group nitride system single crystal, wherein:

the III-V group nitride system semiconductor substrate comprises:

a flat surface; and

an axial orientation of the III-V group nitride system single crystal forms a convergence point at one of inside a plane of the substrate and outside a plane of the substrate such that,

a vector made by projecting on a surface of the substrate a normal vector of a low index surface closest to the substrate surface at an arbitrary point in a plane of the substrate is converged on a specific point or a specific region inside the plane of the substrate.