Semiconductor substrate and method of manufacturing

1. A method for forming a substrate comprising: forming a buffer layer on a substrate wherein the substrate comprises sapphire, and the buffer layer comprises: a first film comprising silicon directly contacting a surface of the substrate; and a second film comprising a Group III-V material directly contacting a surface of the first film; forming a base layer comprising a Group III-V material on the buffer layer; cooling the base layer to induce cracks in the base layer, wherein the cracks are terminated at an interface between the base layer and the buffer layer; and forming a bulk layer comprising a Group III-V material directly on the base layer after cooling, wherein during forming the bulk layer, the cracks induced in the base layer do not substantially propagate into the bulk layer.

2. The method of claim 1 , wherein the base layer comprises gallium nitride.

3. The method of claim 1 , wherein the bulk layer comprises gallium nitride.

4. The method of claim 1 , wherein forming the base layer comprises epitaxial growth of the Group III-V material in a three-dimensional growth mode.

5. The method of claim 1 , wherein forming the base layer comprises epitaxial growth of the Group III-V material in a two-dimensional growth mode.

6. A method for forming a substrate comprising:

forming a buffer layer overlying a substrate comprising sapphire, wherein the buffer layer comprises:

a first film comprising silicon directly contacting a surface of the substrate; and

a second film comprising a Group III-V material directly contacting a surface of the first film;

forming a random array of island features comprising a Group III-V material overlying the buffer layer;

coalescing the random array of island features into a base layer as a continuous layer of uniform thickness comprising the Group III-V material, wherein the base layer comprises an average thickness of at least 0.5 mm to not greater than about 3 mm;

cooling the base layer and forming cracks in the base layer; and

forming a bulk layer comprising a Group III-V material on the base layer after cooling, wherein forming the bulk layer is completed exclusively in a three-dimensional (3D) growth mode.

7. The method of claim 6 , wherein the cracks induced in the base layer do not propagate into the bulk layer.

8. The method of claim 6 , wherein cooling is conducted at a rate of at least about 200° C./hr.

9. The method of claim 6 , wherein the bulk layer comprises an average thickness of at least 1 mm.

10. The method of claim 6 , wherein cooling is conducted in a cooling atmosphere comprising an atmosphere selected from the group consisting of a reducing atmosphere, an oxidizing atmosphere, and an inert atmosphere.

11. The method of claim 5 , wherein the base layer comprises GaN.

12. The method of claim 5 , wherein the bulk layer comprises GaN.

13. The method of claim 1 , wherein forming the bulk layer comprises epitaxial growth of the Group III-V material in a three-dimensional growth mode.

14. The method of claim 1 , further comprising removing the base layer from the bulk layer.

15. The method of claim 14 , wherein removing comprises grinding the base layer from the bulk layer.

16. The method of claim 1 , further comprising finishing an upper surface of the bulk layer.

17. The method of claim 16 , wherein finishing comprises polishing at least one major surface of the bulk layer.

18. The method of claim 1 , wherein cooling is conducted at a rate of at least about 200° C/hr.

19. The method of claim 1 , wherein cooling comprises cooling the base layer to a cooling temperature of less than about 600° C.