Inverted light emitting diode on conductive substrate

1. An electronic device comprising:

a conductive n-type substrate;

an n-type Group III-nitride contact layer in a vertical relationship with said substrate;

a Group III-nitride active region between said n-type substrate and said n-type Group III-nitride contact layer;

at least one p-type layer formed between said n-type Group III-nitride contact layer and said substrate; and

a silicon carbide degenerate junction structure between said n-type Group III-nitride contact layer and said n-type substrate for coupling said n-type Group III-nitride contact layer or said substrate to said p-type layer to thereby permit electric current flow from said substrate to said contact layer.

2. A device according to claim 1 , wherein said degenerate junction structure is adjacent said at least one p-type layer.

3. A device according to claim 1 , wherein the carrier concentration in said silicon carbide degenerate junction structure is above about 1×10 19 cm −3 .

4. A device according to claim 1 wherein said degenerate junction structure is between said substrate and said p-type layer, said degenerate junction structure comprising an n-type degenerate layer adjacent said substrate.

5. A device according to claim 1 wherein said degenerate junction structure is between said n-type contact layer and said active region, said degenerate junction structure comprising an n-type degenerate layer adjacent said contact layer.

6. A device according to claim 1 wherein said degenerate junction structure is thin enough to substantially avoid absorption of light emitted from said active layer.

7. A device according to claim 6 wherein said degenerate junction structure comprises layers that are each less than about 1000 Å thick.

8. A device according to claim 1 wherein said substrate is silicon carbide.

9. A device according to claim 1 wherein said substrate is gallium nitride.

10. A light emitting diode comprising:

a conductive n-type substrate;

an n-type Group III-nitride contact layer in a vertical relationship with said substrate;

a Group III-nitride active region between said n-type substrate and said n-type Group III-nitride contact layer;

at least one p-type layer formed between said n-type Group III-nitride contact layer and said substrate; and

a silicon carbide degenerate junction structure between said n-type Group III-nitride contact layer and said n-type substrate for coupling said n-type Group III-nitride contact layer or said substrate to said p-type layer to thereby permit electric current flow from said substrate to said contact layer.

11. A light emitting diode according to claim 10 wherein said degenerate junction structure is adjacent said at least one p-type layer.

12. A light emitting diode according to claim 11 , wherein said degenerate junction structure is between said substrate and said p-type layer, said degenerate junction structure comprising an n-type degenerate layer adjacent said substrate.

13. A light emitting diode according to claim 11 wherein said degenerate junction structure is between said n-type contact layer and said active region, said degenerate junction structure comprising an n-type degenerate layer adjacent said contact layer.

14. A light emitting diode comprising:

an n-type silicon carbide substrate;

a degeneratively-doped n-type silicon carbide epilayer on said substrate;

a degeneratively-doped p-type silicon carbide epilayer on said degeneratively-doped n-type SiC epilayer, said degeneratively-doped epilayers being sufficiently doped to permit quantum mechanical tunneling of carriers between said degeneratively-doped p-type epilayer and said degeneratively-doped n-type epilayer;

a p-type layer on said degeneratively-doped p-type epilayer;

anactive region of Al x In y Ga 1-x-y N where 0≦x≦1, 0≦y≦1 and 0≦x+y≦1 adjacent said p-type layer;

an n-type layer of Al x In y Ga j-x-y N where 0≦x≦1, and 0≦y≦1, and 0≦x+y≦1 adjacent said active region; and

ohmic contacts to said substrate and to said n-type layer.

15. A light emitting diode according to claim 14 wherein said substrate comprises a single crystal selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

16. A light emitting diode according to claim 14 wherein the carrier concentration in said degeneratively-doped layers is above about 1×10 19 cm −3 .

17. A light emitting diode comprising:

an n-type silicon carbide substrate;

a Group III-nitride active region;

an n-type Group III-nitride contact layer in vertical relationship to said substrate and said active layer;

at least one p-type layer for supplying holes to said active region when current is passed through said light emitting diode; and

a tunnel diode structure between said n-type substrate and said n-type contact layer for permitting current to flow from said substrate to said contact layer, wherein said tunnel diode comprises adjacent n-type and p-type degenerately doped silicon carbide layers, said degenerate layers being sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type degenerate layer and said n-type degenerate layer.

18. A light emitting diode according to claim 17 wherein:

said tunnel diode structure is on said substrate;

said n-type layer of said tunnel diode is adjacent said substrate;

said at least one p-type layer is on said p-type layer of said tunnel diode;

said active layer is on said at least one p-type layer; and

said n-type Group III-nitride contact layer is on said active layer.

19. A light emitting diode according to claim 17 wherein:

said p-type layer is on said active region;

said tunnel diode structure is on said at least one p-type layer;

said p-type layer of said tunnel diode is adjacent said at least one p-type layer; and

said n-type layer of said tunnel diode structure is adjacent said n-type contact layer.

20. A device according to claim 1 , wherein said coupling means comprises:

a first patterned metal layer on said substrate, said metal layer forming an ohmic contact to said substrate; and

a second patterned metal layer on said first metal layer.

21. A device according to claim 1 , wherein said coupling means comprises:

a first patterned metal layer on said p-type layer, said metal layer forming an ohmic contact to said p-type layer; and

a second patterned metal layer on said first metal layer.

22. A device according to claim 1 , wherein said first metal layer comprises stripes oriented along a <1 1 00> direction of said substrate.

23. An electronic device according to claim 1 , wherein said silicon carbide degenerate junction structure comprises a p-type silicon carbide degenerate layer on said p-type layer and an n-type silicon carbide degenerate layer adjacent said p-type silicon carbide degenerate layer.

24. An electronic device according to claim 23 , wherein said degenerate layers are sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type silicon carbide degenerate layer and said n-type silicon carbide degenerate layer.

25. A light emitting diode according to claim 10 , wherein said silicon carbide degenerate junction structure comprises a p-type silicon carbide degenerate layer on said p-type layer and an n-type silicon carbide degenerate layer adjacent said p-type silicon carbide degenerate layer.

26. A light emitting diode according to claim 25 , wherein said degenerate layers are sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type silicon carbide degenerate layer and said n-type silicon carbide degenerate layer.

27. An electronic device comprising:

a Group III-nitride active region;

at least one p-type layer on said active region; and

a silicon carbide degenerate junction structure on said p-type layer, wherein said degenerate junction structure is reverse-biased when the electronic device is forward biased with current flowing from said p-type layer to said active region.

28. An electronic device according to claim 27 , wherein said silicon carbide degenerate junction structure comprises a p-type silicon carbide degenerate layer on said p-type layer and an n-type silicon carbide degenerate layer adjacent said p-type silicon carbide degenerate layer.

29. An electronic device according to claim 28 , wherein said degenerate layers are sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type silicon carbide degenerate layer and said n-type silicon carbide degenerate layer.

30. An electronic device according to claim 27 , further comprising:

a conductive n-type substrate;

an n-type Group III-nitride contact layer in a vertical relationship with said substrate, wherein said Group III-nitride active region is between said substrate and said contact layer, said p-type layer is between said active region and said substrate; and said degenerate junction structure is between said p-type layer and said substrate.

31. An electronic device according to claim 30 , wherein said silicon carbide degenerate junction structure comprises a p-type silicon carbide degenerate layer on said p-type layer and an n-type silicon carbide degenerate layer adjacent said p-type silicon carbide degenerate layer.

32. An electronic device according to claim 31 , wherein said degenerate layers are sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type silicon carbide degenerate layer and said n-type silicon carbide degenerate layer.

33. An electronic device according to claim 27 , further comprising:

a conductive n-type substrate;

an n-type Group III-nitride contact layer in a vertical relationship with said substrate, wherein said Group III-nitride active region is between said substrate and said contact layer, said p-type layer is between said active region and said contact layer, and said degenerate junction structure is on said p-type layer.

34. An electronic device according to claim 33 , wherein said silicon carbide degenerate junction structure comprises a p-type silicon carbide degenerate layer on said p-type layer and an n-type silicon carbide degenerate layer adjacent said p-type silicon carbide degenerate layer.

35. An electronic device according to claim 34 , wherein said degenerate layers are sufficiently doped to permit quantum mechanical tunneling of carriers between said p-type silicon carbide degenerate layer and said n-type silicon carbide degenerate layer.