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1. (WO2007005074) GROUP III NITRIDE LAYERS ON SILICON CARBIDE SUBSTRATES
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THAT WHICH IS CLAIMED IS:

1. A semiconductor device structure, comprising:
a silicon carbide (SiC) substrate; and
a Group III nitride epitaxial layer above the SiC substrate having a dislocation density of less than about 4x10 cm" and an isolation voltage of at least about 50V.

2. A semiconductor device structure, comprising:
a silicon carbide (SiC) substrate; and
a Group III nitride epitaxial layer above the SiC substrate and having a thickness sufficient to impart to the Group III nitride layer a dislocation density of less than about 4x108 cm'2, wherein the Group III nitride layer further comprises a transition metal dopant in an amount sufficient to increase the isolation voltage of the Group III nitride epitaxial layer as compared to a Group III nitride layer epitaxial layer of the same thickness without the transition metal dopant.

3. A semiconductor device structure, comprising:
a silicon carbide (SiC) substrate; and
a Group III nitride epitaxial layer above the SiC substrate having a thickness of at least about 5 microns and a dislocation density of less than about 4x108 cm"2.

4. The semiconductor device structure of any of Claims 1, 2 or 3, wherein the Group III nitride epitaxial layer has a dislocation density of less than about 3xlO8 cm"2.

5. The semiconductor device structure of Claim 4, wherein the Group III nitride epitaxial layer has a dislocation density of less than about 2x108 cm"2.

6. The semiconductor device structure of Claim 5, wherein the Group III nitride epitaxial layer has a dislocation density of less than about 108 cm"2.

7. The semiconductor device structure of any of Claims 2 or 3, wherein the Group III nitride epitaxial layer has a voltage of at least about 50V.

8. The semiconductor device structure of any of Claims 1 or 7, wherein the Group III nitride epitaxial layer has a voltage of at least about 100V.

9. The semiconductor device structure of Claim 8, wherein the Group III nitride epitaxial layer has a voltage of at least about 150V.

10. The semiconductor device structure of any of Claims 1 or 2, wherein the Group III nitride epitaxial layer has a thickness of at least about 5 microns.

11. The semiconductor device structure of any of Claims 3 or 10, wherein the Group III nitride epitaxial layer has a thickness of at least about 6 microns.

12. The semiconductor device structure of Claim 11 , wherein the Group III nitride epitaxial layer has a thickness of at least about 8 microns.

13. The semiconductor device structure of Claim 12, wherein the Group III nitride epitaxial layer has a thickness of at least about 10 microns.

14. The semiconductor device structure of Claim 13, wherein the Group III nitride epitaxial layer has a thickness of at least about 20 microns.

15. The semiconductor device structure of any of Claims 1 or 3, wherein the Group III nitride epitaxial layer comprises a transition metal dopant in an amount sufficient to increase the isolation voltage of the Group III nitride epitaxial layer as compared to a Group III nitride epitaxial layer of the same thickness without the transition metal dopant.

16. The semiconductor device structure of any of Claims 2 or 15, wherein the Group III nitride epitaxial layer comprises a transition metal dopant in an amount of at least about 2x1016 cm"3.

17. The semiconductor device structure of Claim 16, wherein the Group III nitride epitaxial layer comprises a transition metal dopant in an amount up to about

2x1018 cm"3.

18. The semiconductor device structure of any of Claims 2 or 15, wherein the transition metal dopant is selected from the group consisting of Fe, Co, Mn, Cr, V, Cu and Ni and mixtures thereof.

19. The semiconductor device structure of Claim 18, wherein the transition metal dopant comprises Fe.

20. The semiconductor device structure of any of Claims 1, 2, or 3, wherein the Group III nitride epitaxial layer comprises gallium nitride (GaN).

21. The semiconductor device structure of any of Claims 1, 2, or 3, wherein the device comprises a device wafer having a diameter of at least about 3 inches.

22. The semiconductor device structure of any of Claims 1 , 2, or 3, wherein the device comprises a device wafer having a diameter of at least about 100 millimeters.

23. The semiconductor device stricture of any of Claims 1, 2, or 3, further comprising at least one nucleation layer disposed between the SiC substrate and the Group III nitride epitaxial layer.

24. The semiconductor device structure of Claim 23, wherein the nucleation layer is selected from the group consisting of aluminum gallium nitride (AlGaN) layers and aluminum nitride (AlN) layers.

25. The semiconductor device structure of any of Claims 1, 2, or 3, wherein the Group III nitride layer comprises a first Group III nitride layer and wherein the device structure further comprises a second Group III nitride epitaxial layer on the first Group III nitride layer to having a composition sufficiently different from said first Group III nitride layer to form a heterostructure and to generate a two dimensional electron gas at the interface between the first and second Group III nitride layers.

26. The semiconductor device structure of Claim 25, further comprising at least a third Group III nitride epitaxial layer above the second Group III nitride layer for increasing the electron mobility in the two dimensional electron gas.

27. The semiconductor device structure of Claim 26, wherein the first Group III nitride layer comprises gallium nitride (GaN), the second Group III nitride epitaxial layer comprises AlxGa1 -XN, wherein 0<x<l, and the third Group III nitride epitaxial layer comprises aluminum gallium nitride having different atomic fractions of aluminum and gallium from the second Group III nitride epitaxial layer.

28. The semiconductor device structure of any of Claims 1, 2, or 3, further comprising at least one strain management layer disposed between the SiC substrate and the Group III nitride epitaxial layer having an associated strain selected to minimize cracking of the Group III nitride layer.

29. The semiconductor device structure of any of Claims 1, 2, or 3, wherein the SiC substrate comprises a single crystal SiC crystal substrate having a polytype selected from the 3C, 4H, 6H and 15Rpolytypes of silicon carbide.

30. The semiconductor device structure of any of Claims 1, 2, or 3, wherein the silicon carbide substrate is not patterned.

31. A semiconductor device structure of Claim 25, further comprising a plurality of respective source, drain and gate contacts in conductive relationship to the heterostructure.

32. The semiconductor device structure of any of Claims 1, 2 or 3, wherein the Group III nitride epitaxial layer has a thickness of at least about 6 microns and an isolation voltage of at least about 50V.

33. A method of fabricating a Group III nitride semiconductor device structure, comprising forming a Group III nitride epitaxial layer having a dislocation density of less than about 4x108 cm"2 and an isolation voltage of at least about 50V on a SiC substrate.
34. A method of fabricating a Group III nitride semiconductor device structure, comprising forming a Group IfI nitride epitaxial layer having a thickness of at least about 5 microns and a dislocation density of less than about 4x10 cm" on a SiC substrate.

35. The method of any of Claims 33 and 34, wherein the forming step comprises forming a Group III nitride epitaxial layer having a dislocation density of less than about 3xlO8 cm"2.

36. The method of Claim 36, wherein the forming step comprises forming a Group III nitride epitaxial layer having a dislocation density of less than about 2xlO8 cm"2.

37. The method of Claim 35, wherein the forming step comprises forming a Group III nitride epitaxial layer having a dislocation density of less than about 108 cm"2.

38. The method of Claim 34, wherein the forming step comprises forming a Group III nitride epitaxial layer having a voltage of at least about 50V.

39. The method of any of Claims 33 or 38, wherein the forming step comprises forming a Group III nitride epitaxial layer having a voltage of at least about 100V.
40. The method of Claim 39, wherein the forming step comprises forming a Group III nitride epitaxial layer having a voltage of at least about 150V.

41. The method of Claim 33, wherein the forming step comprises forming a Group III nitride epitaxial layer having a thickness of at least about 5 microns.

42. The method of any of Claims 34 or 41 , wherein the forming step comprises forming a Group III nitride epitaxial layer having a thickness of at least about 6 microns.

43. The method of Claim 42, wherein the forming step comprises forming a Group III nitride epitaxial layer having a thickness of at least about 8 microns.

44. The method of Claim 43, wherein the forming step comprises forming a Group III nitride epitaxial layer having a thickness of at least about 10 microns.

45. The method of Claim 44, wherein the forming step comprises forming a Group III nitride epitaxial layer having a thickness of at least about 20 microns.

46. The method of any of Claims 33 or 34, wherein the forming step comprises introducing gaseous Group III nitride precursors and a transition metal dopant in an amount sufficient to increase the isolation voltage of the Group III nitride epitaxial layer as compared to a Group III nitride epitaxial layer of the same thickness without a transition metal dopant into a reactor chamber under condition suitable for the epitaxial growth of a Group III nitride epitaxial layer.

47. The method of Claim 46, wherein the introducing step comprises introducing the transition metal dopant in an amount of at least about 2xlO16 cm"3.

48. The method of Claim 47, wherein the introducing step comprises introducing the transition metal dopant in an amount up to about 2x1018 cm"3.

49. The method of Claim 46, wherein the step of introducing gaseous Group III nitride precursors comprises introducing gaseous gallium nitride (GaN) precursors.

50. The method of Claim 49, wherein the GaN precursors comprise gallium trialkyls and ammonia.

51. The method of Claim 46, wherein the step of introducing a transition metal dopant comprises introducing at least one transition metal selected from the group consisting of Fe, Co, Mn, Cr, V, Cu and Ni and mixtures thereof.

52. The method of Claim 51 , wherein the transition metal dopant comprises Fe.

53. The method of any of Claims 33 or 34, further comprising forming at least one nucleation layer between the SiC substrate and the Group III nitride epitaxial layer.

54. The method of any of Claims 33 or 34, wherein the Group III nitride layer is a first Group III nitride layer and wherein the method further comprises forming a heterostructure comprising the first Group III nitride and a second Group III nitride epitaxial layer on the first Group III nitride layer having a composition sufficiently different from the first Group III nitride layer to generate a two dimensional electron gas at the interface between the first and second Group III nitride layers.

55. The method of Claim 54, further comprising forming at least a third Group III nitride epitaxial layer above the second Group III nitride layer for increasing the electron mobility in the two dimensional electron gas.

56. The method of Claim 55, wherein the first Group III nitride layer comprises gallium nitride (GaN), the second Group III nitride epitaxial layer comprises AlxGa1 -XN, wherein 0<x<l, and the third Group III nitride epitaxial layer comprises aluminum gallium nitride having different atomic fractions of aluminum and gallium from the second Group III nitride epitaxial layer.

57. The method of any of Claims 33 or 34, further comprising forming at least one strain management layer between the SiC substrate and the Group III nitride epitaxial layer having an associated strain selected to minimize cracking of the Group in nitride layer.

58. The method of Claim 54, further comprising forming a plurality of gate, source and drain contacts in conductive relationship to the heterostructure.

59. The method of any of Claims 33 or 34, wherein the forming step comprises forming a Group III nitride epitaxial layer on an unpatterned silicon carbide substrate.