HIGH EFFICIENCY GROUP III NITRIDE LED WITH LENTICULAR SURFACE

• US 20110284875A1
• Filed: 07/21/2011
• Published: 11/24/2011
• Est. Priority Date: 09/22/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John Adam, Slater, David Beardsley JR., Donofrio, Matthew, Bharathan, Jayesh
• Granted Patent: US 8,692,267 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating

Abstract

A high efficiency Group III nitride light emitting diode is disclosed. The diode includes a substrate selected from the group consisting of semiconducting and conducting materials, a Group III nitride-based light emitting region on or above the substrate, and, a lenticular surface containing silicon carbide on or above the light emitting region, and extending to said light emitting region.

Claims

1. A high efficiency Group III nitride light emitting diode comprising:

a substrate selected from the group consisting of semiconducting and conducting materials;

a Group III nitride-based light emitting region on said substrate; and

a lenticular surface extending to said light emitting region.

2. A light emitting diode according to claim 1, wherein said lenticular surface extends to, but not beyond, said light emitting region.

3. A light emitting diode according to claim 1 wherein said lenticular surface extends into said light emitting region.

4. A light emitting diode of claim 1, wherein said lenticular surface contains silicon carbide.

5. A light emitting diode according to claim 1 wherein said lenticular surface comprises single crystal silicon carbide.

6. A light emitting diode according to claim 1 further comprising an ohmic contact to said substrate and an ohmic contact to said Group III nitride emitting region.

7. A light emitting diode according to claim 1 further comprising a phosphor-containing structure adjacent said lenticular surface for converting emissions from said light emitting region into frequencies that will produce white light.

8. A light emitting diode according to claim 1 wherein said lenticular surface comprises a plurality of cones.

9. A light emitting diode according to claim 1 wherein said lenticular surface comprises a plurality of pyramids.

10. A light emitting diode according to claim 1 comprising at least one p-type layer of Group III nitride and at least one n-type layer of Group III nitride for current injection and recombination of carriers in said light emitting region.

11. A light emitting diode according to claim 10 wherein said Group III nitride-based light emitting region comprises at least one of said p-type or n-type layers.

12. A light emitting diode according to claim 1 wherein said Group III nitride based light emitting region comprises a mesa structure.

13. A light emitting diode according to claim 12 comprising a passivation layer on at least portions of said mesa.

14. A light emitting diode according to claim 12 comprising a passivation layer on at least portions of said mesa and on at least portions of said lenticular surface.

15. A high efficiency Group III nitride light emitting diode comprising:

a conductive silicon carbide substrate;

an aluminum indium gallium nitride light emitting region on said substrate; and

a thin lenticular surface of silicon carbide on said light emitting region and having features extending to said light emitting region.

16. A light emitting diode according to claim 15 wherein said lenticular surface features extend to but not into said light said light emitting region.

17. A light emitting diode according to claim 15 wherein said lenticular surface features extend into said light emitting region.

18. A light emitting diode according to claim 15 comprising a light emitting layer, at least one p-type layer of Group III nitride and at least one n-type layer of Group III nitride for current injection and recombination of carriers in said light emitting layer.

19. A light emitting diode of claim 18 wherein said lenticular surface features extend into said p-type or n-type layers.

20. The light emitting diode of claim 18, wherein said lenticular surface features extend into said p-type or n-type layers, but not into said light emitting layer.

21. A high efficiency Group III nitride light emitting diode comprising:

a substrate selected from the group consisting of conducting and semiconducting materials;

at least one metal bonding layer on one surface of said substrate;

an ohmic contact to the opposite surface of said substrate from said metal layer;

a light emitting structure based upon the Group III nitride system on said at least one metal layer on said substrate;

an ohmic contact on said light emitting structure opposite said substrate; and

a lenticular surface having features extending to said light emitting structure, at least portions of which are formed of silicon carbide, on the portions of said light emitting structure other than said ohmic contact.

22. A light emitting diode according to claim 21, wherein said lenticular surface features extend to, but not into, said light emitting structure.

23. A light emitting diode according to claim 21 wherein said lenticular surface features extend into said light emitting region.

24. A light emitting diode according to claim 23 wherein said Group III nitride light emitting structure includes at least a light emitting layer and respective layers of p-type Group III nitride and n-type Group III nitride sandwiching said light emitting layer, said lenticular surface not extending into said light emitting layer.

25. A light emitting diode according to claim 21 comprising a mirror layer between said light emitting structure and said metal bonding layer for enhancing the light extraction from the diode.

26. A light emitting diode according to claim 21 wherein said lenticular surface is formed of portions of silicon carbide and portions of said light emitting structure.

27. A light emitting diode according to claim 21 wherein said lenticular surface is formed of a plurality of cones.

28. A light emitting diode according to claim 21 wherein said lenticular surface is formed of a plurality of pyramids selected from the group consisting of four-sided pyramids, six-sided pyramids and combinations thereof.

29. A high efficiency Group III nitride light emitting diode comprising:

a silicon carbide substrate;

a backside ohmic contact on one surface of said substrate for providing one electrical connection to said diode;

a metal bonding layer on the opposite surface of said substrate for providing a physical and electronic transition between said substrate and other portions of said diode;

a mirror layer on said metal bonding layer for enhancing light extraction from said diode;

a p-type Group III nitride layer on said mirror;

a light emitting Group III nitride layer on said p-type layer and having a bandgap smaller than the bandgap of said p-type layer;

an n-type Group III nitride layer on said light emitting layer and having a bandgap larger than the bandgap of said light emitting layer;

a wire bond pad ohmic contact to said n-type layer for providing a second electrical connection to said diode; and

a lenticular surface, at least portions of which are formed of silicon carbide, on and having features extending to portions of said n-type layer other than said wire bond pad.

30. A light emitting diode according to claim 29, wherein said lenticular surface features extend to, but not into, said n-type layer.

31. A light emitting diode according to claim 29 wherein said lenticular surface features extend into said n-type layer.

32. A high-efficiency Group III nitride light emitting diode package comprising:

a lead frame; and

a light emitting diode on said lead frame;

said diode including,

a substrate selected from the group consisting of semiconducting and conducting materials;

a Group III nitride based light emitting region on said substrate;

a lenticular surface containing silicon carbide on and extending to said light emitting region;

an ohmic contact between said substrate and said lead frame; and

an ohmic contact to said light emitting region.

33. A wafer structure for high efficiency Group III nitride light emitting diode precursors, said wafer structure comprising:

a conductive silicon carbide substrate wafer;

a Group III nitride epitaxial layer on said substrate;

a plurality of discrete ohmic contacts on the surface of said Group III nitride epitaxial layer, said ohmic contacts defining a plurality of discrete light emitting diode precursors; and

a lenticular surface containing silicon carbide and on said Group III nitride epitaxial layer, said lenticular surface having features extending to said epitaxial layer.