LIGHT EMITTING DIODE WTH DEGENERATE COUPLING STRUCTURE

• US 20070114541A1
• Filed: 01/22/2007
• Published: 05/24/2007
• Est. Priority Date: 02/14/2003
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John, Kong, Hua-Shuang, Bergmann, Michael, Doverspike, Kathleen
• Granted Patent: US 7,482,183 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 33/0004 Devices characterised by their operation
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/145 with a current-blocking structure

Abstract

An electronic device includes a conductive n-type substrate, a Group III nitride active region, an n-type Group III-nitride layer in vertical relationship to the substrate and the active layer, at least one p-type layer, and means for providing a non-rectifying conductive path between the p-type layer and the n-type layer or the substrate. The non-rectifying conduction means may include a degenerate junction structure or a patterned metal layer.

Claims

1. A method of forming a light emitting device (LED) that incorporates a Group III nitride layer, the method comprising:

forming an n-type Group III nitride active region on an n-type semiconductor layer;

forming a p-type semiconductor layer on the active region;

forming a degenerate junction structure on the p-type semiconductor layer;

forming an n-type contact layer on the degenerate junction structure, wherein the degenerate junction structure includes at least one p-n junction for coupling the p-type semiconductor layer to the n-type contact layer to thereby permit electric current flow from the n-type contact layer to the active region.

2. A method of forming an LED according to claim 1 wherein the step of forming the degenerate junction structure comprises forming a p-n junction structure from a degeneratively-doped p-type silicon carbide epilayer on the p-type semiconductor layer and a degeneratively-doped n-type silicon carbide epilayer on the p-type silicon carbide epilayer.

3. A method of forming an LED according to claim 1 wherein the carrier concentration in the degeneratively doped p-njunction structure is above about 1×

10¹⁹ cm<sup>−

3</sup>.

4. A method of forming an LED according to claim 2, wherein the step of forming the p-type epilayer comprises forming a layer of silicon carbide doped with aluminum.

5. A method o forming an LED according to claim 2, wherein the step of forming the n-type epilayer comprises forming a layer of silicon carbide doped with a dopant selected from the group consisting of nitrogen and phosphorous.

6. A method of forming an LED according to claim 1 wherein the step of forming the degenerate junction structure comprises forming a p-n junction structure from a degeneratively-doped p-type Group III nitride epilayer on the p-type semiconductor layer and a degeneratively-doped n-type Group III nitride epilayer on the p-type silicon carbide epilayer.

7. A method of forming an LED according to claim 1 wherein the carrier concentration in each layer of the degeneratively doped p-n junction structure is above about 1×

10¹⁹ cm<sup>−

3</sup>.

8. A method of forming an LED according to claim 1 wherein the step of forming the degenerate junction structure comprises forming a p-n junction structure from a degeneratively-doped p-type Group II-VI epilayer on the p-type semiconductor layer and a degeneratively-doped n-type Group II-VI epilayer on the p-type Group II-VI carbide epilayer.

9. A method of forming an LED according to claim 8 wherein the carrier concentration in each layer of the degeneratively doped p-n junction structure is above about 1×

10¹⁹ cm<sup>−

3</sup>.

10. A method of forming an LED according to claim 1 wherein step of forming the degenerate junction structure comprises forming a p-type semiconductor layer and an n-type semiconductor layer, both of which are thin enough to substantially avoid absorption of light emitted from the active region.

11. A method of forming an LED according to claim 10 wherein the step of forming the degenerate junction structure comprises forming layers of a p-type epilayer and an n-type epilayer that are each less than about 1000 Å

thick.

12. A method of forming an LED according to claim 1, wherein the step of forming the active region comprises forming the n-type semiconductor layer on a substrate, wherein the substrate comprises a single crystal silicon carbide selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

13. A method of forming an LED according to claim 1, wherein the step of forming the active region comprises forming the n-type semiconductor layer on a substrate, wherein the substrate comprises a Group III nitride layer.

14. A method of forming a light emitting device (LED) that incorporates a Group III nitride layer, the method comprising:

forming a degenerate junction structure on an n-type semiconductor layer, wherein the degenerate junction structure comprises a degenerately doped n-type epilayer on the n-type semiconductor layer and a degenerately doped p-type epilayer on the n-type epilayer;

forming a p-type semiconductor layer on the p-type epilayer of the degenerate junction structure;

forming an n-type Group III nitride active region on the p-type semiconductor layer;

forming an n-type semiconductor contact layer on the active region;

wherein the degenerate junction structure couples the p-type semiconductor layer to the LED anode to thereby permit electric current flow from the anode to the active region.

15. A method of forming an LED according to claim 14 wherein the carrier concentration in each layer of the degenerate junction structure is above about 1×

10¹⁹ cm<sup>−

3</sup>.

16. A method of forming an LED according to claim 14, wherein the step of forming the p-type epilayer comprises forming a layer of silicon carbide doped with aluminum.

17. A method of forming an LED according to claim 14, wherein the step of forming the n-type epilayer comprises forming a layer of silicon carbide doped with a dopant selected from the group consisting of nitrogen and phosphorous.

18. A method of forming an LED according to claim 14, wherein the step of forming the degenerate junction structure comprises forming a p-n junction structure from a degeneratively-doped n-type Group III nitride epilayer on the n-type semiconductor layer and a degeneratively-doped p-type Group III nitride epilayer on the n-type silicon carbide epilayer.

19. A method of forming an LED according to claim 14, wherein the step of forming the degenerate junction structure comprises forming a p-n junction structure from a degeneratively-doped n-type Group II-VI epilayer on the n-type semiconductor layer and a degeneratively-doped p-type Group II-VI epilayer on the n-type Group II-VI epilayer.

20. A method of forming an LED according to claim 14 wherein step of forming the degenerate junction structure comprises forming the p-type epilayer and the n-type epilayer to a combined thickness that substantially avoids absorption of light emitted from the active region.

21. A method of forming an LED according to claim 22 wherein the step of forming the degenerate junction structure comprises forming layers of a p-type epilayer and an n-type epilayer that are each less than about 1000 Å

thick.

22. A method of forming an LED according to claim 14, wherein the step of forming the degenerate junction structure comprises forming the degenerate junction structure on a substrate comprising a single crystal silicon carbide selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

23. A method of forming an LED according to claim 14, wherein the step of forming the degenerate junction structure comprises forming the degenerate junction structure on a substrate comprising a Group III nitride layer.

24. A method of forming a light emitting device (LED) that conducts a forward biased electrical current from the anode contact to the cathode contact, comprising:

forming a Group III nitride active region for light emission from the LED;

forming a minority carrier source layer adjacent the active region for injecting minority carriers into the active region;

forming a tunnel diode structure adjacent the minority carrier source layer, the tunnel diode structure having a degenerately doped n-type semiconductor epilayer and a degenerately doped p-type semiconductor epilayer that permit quantum mechanical tunneling of carriers between the epilayers of the tunnel diode; and

positioning the tunnel diode structure between layers of the LED having opposite conductivity type to thereby permit electric current flow from the minority carrier source layer to the cathode of the device.

26. A method of forming an LED according to claim 26 wherein the carrier concentration in each layer of the tunnel diode is above about 1×

10¹⁹ cm<sup>−

3</sup>.

25. A method of forming an LED according to claim 26, wherein the step of positioning the tunnel diode comprises forming the p-type epilayer of the tunnel diode on the minority carrier source layer.

27. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming a degenerate p-type epilayer of silicon carbide doped with aluminum.

28. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming a degenerate n-type epilayer of silicon carbide doped with a dopant selected from the group consisting of nitrogen and phosphorous.

29. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming a p-n junction structure of doped Group III nitride epilayers.

30. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming a p-n junction structure of doped Group II-VI epilayers.

31. A method of forming an LED according to claim 26 wherein step of forming the tunnel diode comprises forming the p-type epilayer and the n-type epilayer to a total thickness that substantially avoids absorption of light emitted from the active region.

32. A method of forming an LED according to claim 26 wherein the step of forming the tunnel diode comprises forming layers of a p-type epilayer and an n-type epilayer that are each less than about 1000 Å

thick.

33. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming the tunnel diode on a substrate comprising a single crystal silicon carbide selected from the group consisting of the 3C, 4H, 6H, and 15R polytypes.

34. A method of forming an LED according to claim 26, wherein the step of forming the tunnel diode comprises forming the tunnel diode on a substrate comprising a Group III nitride layer.