III-nitride heterojunction semiconductor device and method of fabrication

1. A III-nitride power semiconductor device comprising:

an active III-nitride heterojunction that includes a III-nitride channel layer and a III-nitride barrier layer formed on said channel layer to generate a two-dimensional electron gas, said III-nitride barrier layer including a region therein having a nitrogen content that is less than the rest of said barrier layer;

a gate coupled to said III-nitride heterojunction;

a first power electrode coupled to said III-nitride heterojunction; and

a second power electrode coupled to said III-nitride heterojunction, wherein either said gate or one of said power electrodes is disposed over said region having a nitrogen content that is less than the rest of said barrier layer.

2. The device of claim 1 , wherein said barrier layer is comprised of AlGaN and said channel layer is comprised of GaN.

3. The device of claim 1 , wherein said power electrodes are coupled to said barrier layer.

4. The device of claim 1 , wherein said gate includes a gate electrode schottky coupled to said III-nitride heterojunction.

5. The device of claim 4 , wherein said gate electrode is schottky coupled to said barrier layer.

6. The device of claim 1 , wherein said gate includes a gate electrode and a gate dielectric disposed between said gate electrode and said III-nitride heterojunction.

7. The device of claim 6 , wherein said gate dielectric is disposed between said gate electrode and said barrier layer.

8. The device of claim 1 , wherein said III-nitride heterojunction is disposed over a support body that includes a silicon substrate, and a III-nitride transition layer.

9. The device of claim 8 , wherein said transition layer is comprised of AlN.

10. The device of claim 1 , wherein said III-nitride heterojunction is disposed over a support body that includes a substrate, and a transition layer, said substrate being composed of one of SiC and sapphire.

11. A III-nitride power semiconductor device comprising:

a III-nitride heterojunction comprising a II-nitride channel layer and a III-nitride barrier layer over said channel layer to generate a two-dimensional electron gas;

said III-nitride barrier layer having a reduced nitrogen content region under a gate of said III-nitride power semiconductor device so as to increase carrier concentration under said gate, and to thereby reduce a conduction resistance of said channel layer.

12. The III-nitride power semiconductor device of claim 11 , further comprising:

a first power electrode disposed over said III-nitride heterojunction.

13. The III-nitride power semiconductor device of claim 12 , further comprising:

a second power electrode disposed over said III-nitride heterojunction.

14. The III-nitride power semiconductor device of claim 11 , wherein said barrier layer is comprised of AlGaN.

15. The III-nitride power semiconductor device of claim 11 , wherein said channel layer is comprised of GaN.

16. A III-nitride power semiconductor device comprising:

a III-nitride heterojunction comprising a III-nitride channel layer and a III-nitride barrier layer formed over said channel layer to generate a two-dimensional electron gas;

said III-nitride barrier layer having a reduced nitrogen content region under a gate of said III-nitride power semiconductor device so as to increase relative aluminum concentration, and to thereby render said reduced nitrogen content region less conductive.

17. The III-nitride power semiconductor device of claim 16 , wherein said III-nitride power semiconductor device is an enhancement mode device.

18. The III-nitride power semiconductor device of claim 16 , further comprising:

a first power electrode and a second power electrode disposed over said III-nitride heterojunction.

19. The III-nitride power semiconductor device of claim 16 , wherein said barrier layer is comprised of AlGaN.

20. The III-nitride power semiconductor device of claim 16 , wherein said channel layer is comprised of GaN.