III-nitride semiconductor device

1. A III-nitride power semiconductor device comprising:

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

said III-nitride barrier layer being decomposed so as to achieve a reduced nitrogen region in said III-nitride barrier layer, compared to an adjoining region of said III-nitride barrier layer;

said reduced nitrogen region situated in said III-nitride barrier layer and substantially confined under at least one of a gate, a source electrode, and a drain electrode of said III-nitride power semiconductor device such that said reduced nitrogen region does not extend between said gate and either of said source electrode and said drain electrode, said reduced nitrogen region having an increased group III semiconductor concentration compared to said adjoining region of said III-nitride barrier layer.

2. The III-nitride power semiconductor device of claim 1 , wherein said gate of said III-nitride power semiconductor device is disposed over said reduced nitrogen region.

3. The III-nitride power semiconductor device of claim 1 , wherein at least one of said source electrode and said drain electrode of said III-nitride power semiconductor device is disposed over said reduced nitrogen region.

4. The III-nitride power semiconductor device of claim 1 , wherein said III-nitride barrier layer comprises AlGaN.

5. The III-nitride power semiconductor device of claim 1 , wherein said III-nitride channel layer comprises GaN.

6. A III-nitride power semiconductor device comprising:

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

said III-nitride barrier layer being decomposed so as to achieve a reduced thickness region in said III-nitride barrier layer and substantially confined under at least one of a gate, a source electrode, and a drain electrode of said III-nitride power semiconductor device such that said reduced thickness region does not extend between said gate and either of said source electrode and said drain electrode;

wherein a thickness of said reduced thickness region is less than a thickness of said III-nitride barrier layer, said reduced thickness region having an increased group III semiconductor concentration compared to an adjoining region of said III-nitride barrier layer.

7. The III-nitride power semiconductor device of claim 6 , wherein said gate of said III-nitride power semiconductor device is disposed over said reduced thickness region.

8. The III-nitride power semiconductor device of claim 6 , wherein at least one of said source electrode and said drain electrode of said III-nitride power semiconductor device is disposed over said reduced thickness region.

9. The III-nitride power semiconductor device of claim 6 , wherein said III-nitride barrier layer comprises AlGaN.

10. The III-nitride power semiconductor device of claim 6 , wherein said III-nitride channel layer comprises GaN.

11. A III-nitride power semiconductor device comprising:

a III-nitride heterojunction that includes a III-nitride channel layer and a III-nitride barrier layer formed over said channel layer to generate a two-dimensional electron gas, said HI-nitride barrier layer being decomposed so as to have reduced nitrogen region situated therein, compared to an adjoining region of said III-nitride barrier layer, said reduced nitrogen region having an increased group III semiconductor concentration compared to said adjoining region of said III-nitride barrier layer;

first and second power electrodes being coupled to said III-nitride heterojunction;

a gate situated between said first and second power electrodes, said gate coupled to said III-nitride heterojunction, wherein said gate is disposed directly over said reduced nitrogen region, said reduced nitrogen region being substantially confined under said gate such that said reduced nitrogen region does not extend between said gate and either of said first and second power electrodes.

12. The III-nitride power semiconductor device of claim 11 , wherein said III-nitride barrier layer comprises of AlGaN and said III-nitride channel layer comprises GaN.

13. The III-nitride power semiconductor device of claim 11 , wherein said gate includes a Schottky gate electrode coupled to said III-nitride heterojunction.

14. The III-nitride power semiconductor device of claim 11 , wherein said gate includes a gate electrode and a gate dielectric disposed between said gate electrode and said III-nitride heterojunction.

15. The III-nitride power semiconductor device of claim 11 , wherein said III-nitride heterojunction is disposed over a support body that includes a silicon substrate and a III-nitride transition layer.

16. The III-nitride power semiconductor device of claim 15 , wherein said transition layer comprises AlN.

17. The III-nitride power semiconductor device of claim 11 , wherein said III-nitride heterojunction is disposed over a support body that includes a substrate and a transition layer, said substrate being selected from the group consisting of SiC and sapphire.