Process for manufacture of super lattice using alternating high and low temperature layers to block parasitic current path

1. A method of fabricating a power field-effect transistor (power FET), comprising:

providing a substrate;

growing a III-nitride body comprising aluminum nitride (AlN) over a major surface of said substrate to a final thickness over a growth period of time, wherein growth temperature is started at a low growth temperature and varied in cycles thereafter over said growth period of time, each cycle including a period of high temperature growth at a high temperature and a period of low temperature growth at a low temperature;

said high temperature and said low temperature converging during said growth period of time until said high temperature and said low temperature are substantially equal to a final growth temperature of said III-nitride body;

said III-nitride body being a superlattice structure wherein a number of layers grown at said high temperature is equal to a number of layers grown at said low temperature;

forming a buffer layer over said III-nitride body;

forming an active layer on said buffer layer, said active layer providing an active region for said power FET;

said buffer layer and said III-nitride body being provided to resist current flow outside said active layer.

2. The method of claim 1 , wherein said low temperature in each cycle is varied.

3. The method of claim 1 , wherein said high temperature in each cycle is varied.

4. The method of claim 1 , wherein said low temperature and said high temperature in each cycle are varied.

5. The method of claim 1 , wherein said high temperature in each cycle is the same.

6. The method of claim 1 , wherein said low temperature in each cycle is the same.

7. The method of claim 1 , wherein said period of said high temperature growth is varied.

8. The method of claim 1 , wherein said period of said low temperature growth is varied.

9. The method of claim 1 , wherein said period of said high temperature growth and said period of said low temperature growth are varied.

10. The method of claim 1 , wherein said period of said high temperature growth is equal to said period of said low temperature growth.

11. The method of claim 1 , wherein said period of said high temperature growth is different than said period of said low temperature growth.

12. The method of claim 1 , wherein said growth temperature is varied continuously.

13. The method of claim 1 , wherein said growth temperature is varied in discrete steps.

14. The method of claim 1 , wherein said high growth temperature and said low growth temperature converge with each growth cycle.

15. The method of claim 1 , wherein the alloy composition of said III-nitride body is varied during said growing step.