Light emitting diode with improved light extraction

• US 8,575,633 B2
• Filed: 12/08/2008
• Issued: 11/05/2013
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Kong, Hua-Shuang, Edmond, John, Slater, David Jr.
• Primary Examiner(s): Luu, Chuong A.
• Application Number:
  US12/329,713
• Publication Number:
  US 20100140636A1
• Time in Patent Office: 1,793 Days
• Field of Search: 257/91, 257/95, 257/98, 257/E33.006, 257/E33.005, 257/99, 257/13, 257/79, 257/82, 257/88, 257/93, 257/96, 257/83, 257/89
• US Class Current: 257/98
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A light emitting diode is disclosed that includes an active region and a plurality of exterior surfaces. A light enhancement feature is present on at least portions of one of the exterior surfaces of the diode, with the light enhancement feature being selected from the group consisting of shaping and texturing. A light enhancement feature is present on at least portions of each of the other exterior surfaces of the diode, with these light enhancement features being selected from the group consisting of shaping, texturing, and reflectors.

Claims

1. A light emitting diode comprising:

a plurality of exterior surfaces;

a light enhancement feature on at least portions of a first one of said exterior surfaces of said diode, said light enhancement feature being selected from the group consisting of shaping and texturing;

a light enhancement feature on at least portions of at least two of each of the other exterior surfaces of said diode, wherein said other exterior surfaces are at least partially integral to components of said light emitting diode that are distinct from the diode component integral to said first exterior surface, said light enhancement features being selected from the group consisting of shaping, texturing, and reflectors;

ohmic contacts in a lateral orientation, each of said ohmic contacts on a first side of said light emitting diode, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature;

an active region formed from the Group III nitride material system;

wherein one of said light enhancement features comprises a reflector; and

wherein one of said exterior surfaces is on the bottom of said light emitting diode.

2. A light emitting diode according to claim 1 further comprising a substrate supporting said active region.

3. A light emitting diode according to claim 2 wherein said substrate is selected from the group consisting of SiC, sapphire, silicon, and metals.

4. A light emitting diode according to claim 1 wherein said active region includes at least one Group III nitride epitaxial layer;

and

wherein at least one light enhancement feature on one of said exterior surfaces is a beveled cut in which said exterior surface defines a non-perpendicular angle with respect to said Group III nitride epitaxial layer.

5. A light emitting diode according to claim 1 wherein one or more of said exterior surfaces include at least two different light enhancement features.

6. A light emitting diode according to claim 1 wherein at least one exterior surface includes a reflector.

7. A light emitting diode according to claim 6 wherein said reflector comprises one or more metal layers.

8. A light emitting diode according to claim 6 wherein said reflector includes a plurality of dielectric layers.

9. A light emitting diode according to claim 8 wherein said reflector further includes one or more metal layers.

10. A light emitting diode according to claim 1 wherein at least one of said light enhancement features is a textured feature selected from the group consisting of mechanically textured features, crystallographic features, and lenticular features.

11. A light emitting diode according to claim 10 wherein said textured surface comprises a random pattern having features on the order of a wavelength of light.

12. A light emitting diode according to claim 1 wherein at least one of said light enhancement features comprises a lenticular surface.

13. A light emitting diode comprising:

a plurality of exterior surfaces;

a light enhancement feature on at least portions of a first one of said exterior surfaces of said diode, said light enhancement feature being selected from the group consisting of shaping and texturing;

a light enhancement feature on at least portions of at least two of each of the other exterior surfaces of said diode, wherein said other exterior surfaces are at least partially integral to components of said light emitting diode that are distinct from the diode component integral to said first exterior surface, said light enhancement features being selected from the group consisting of shaping, texturing, and reflectors, wherein each exterior surface includes a single light enhancement feature;

ohmic contacts in a lateral orientation, each of said ohmic contacts on a first side of said light emitting diode, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature;

wherein one of said light enhancement features comprises a reflector; and

wherein at least one of said exterior surfaces is below a substrate.

14. A light emitting diode comprising:

a substrate;

a Group III nitride active region formed on said substrate, wherein said active region comprises at least one n-type layer and one p-type layer;

said substrate and said Group III nitride active region defining a plurality of exterior surfaces;

one of said exterior surfaces having a light enhancement feature selected from the group consisting of shaping and texturing;

the remainder of said exterior surfaces having light enhancement features selected from the group consisting of shaping, texturing, and reflectors;

ohmic contacts in a lateral orientation on a first surface of said active region, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature;

wherein at least one light enhancement feature on one of said exterior surfaces is a shaped beveled cut in which said exterior surface defines a non-perpendicular angle with respect to said n-type layer; and

wherein at least one of said exterior surfaces is below said substrate.

15. A light emitting diode according to claim 14 wherein said active region further comprises:

an ohmic contact to said n-type layer and an ohmic contact to said p-type layer.

16. A light emitting diode according to claim 14 wherein each exterior surface includes a single light enhancement feature.

17. A light emitting diode according to claim 14 wherein one or more of said exterior surfaces include at least two different light enhancement features.

18. A light emitting diode according to claim 14 wherein at least one exterior surface includes a reflector.

19. A light emitting diode according to claim 18 wherein said reflector is on said substrate opposite said active region.

20. A light emitting diode according to claim 18 wherein said reflector comprises one or more metal layers.

21. A light emitting diode according to claim 18 wherein said reflector includes a plurality of dielectric layers.

22. A light emitting diode according to claim 14 wherein at least one of said light enhancement features comprises texturing.

23. A light emitting diode according to claim 22 where said texturing creates a random pattern having features on the order of a wavelength of light.

24. A light emitting diode according to claim 14 wherein at least one of said light enhancement features comprises a lenticular surface.

25. A light emitting diode according to claim 14 wherein said substrate is selected from the group consisting of SiC, sapphire, silicon, and metals.

26. A light emitting diode comprising:

an active region having at least one n-type layer and one p-type layer wherein said active region includes at least one Group III nitride epitaxial layer;

a plurality of exterior surfaces;

at least four of said exterior surfaces having light enhancement features selected from the group consisting of beveled cuts, texturing, lenticular surfaces, and reflectors;

ohmic contacts in a lateral orientation, each of said ohmic contacts on a first surface of said active region, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature; and

wherein one of said exterior surfaces is on the bottom of said light emitting diode.

27. A light emitting diode according to claim 26 wherein at least two of said surfaces with light enhancement features form angles of between 0°

and 90°

.

28. A light emitting diode according to claim 26 wherein at least two of said surfaces with light enhancement features form angles of between 30°

and 60°

.

29. A light emitting diode according to claim 26 wherein at least six of said exterior surfaces have light enhancement features selected from the group consisting of shaping, texturing, and reflectors.

30. A light emitting diode according to claim 26 having at least eight exterior surfaces that have light enhancement features selected from the group consisting of shaping, texturing, and reflectors.

31. A light emitting diode according to claim 26 wherein at least one light enhancement feature on one of said exterior surfaces is a beveled cut in which said exterior surface defines a non-perpendicular angle with respect to said Group III nitride epitaxial layer.

32. A light emitting diode according to claim 26 wherein one or more of said exterior surfaces include at least two different light enhancement features.

33. A light emitting diode according to claim 26 wherein at least one of said exterior surfaces includes a reflector.

34. A light emitting diode according to claim 26 wherein at least one of said light enhancement features comprises texturing.

35. A light emitting diode according to claim 34 wherein said texturing creates a random pattern having features on the order of a wavelength of light.

36. A light emitting diode according to claim 34 wherein at least one of said light enhancement features comprises a lenticular surface.

37. A light emitting diode according to claim 26 further comprising a substrate selected from the group consisting of SiC, sapphire, silicon, and metals.

38. A light emitting diode comprising:

a plurality of exterior surfaces;

an active region formed from the Group III nitride material system;

ohmic contacts in a lateral orientation, each of said ohmic contacts on a first side of said light emitting diode;

at least one light enhancement feature on at least portions of at least two of said exterior surfaces of said diode, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature;

wherein one of said light enhancement features comprises a reflector; and

wherein one of said exterior surfaces is on the bottom of said light emitting diode.

39. The light emitting diode of claim 38 wherein said light enhancement features comprise shaped surfaces.

40. The light emitting diode of claim 38 wherein said light enhancement features comprise textured surfaces.

41. The light emitting diode of claim 39 wherein said light enhancement features comprise reflectors.

42. The light emitting diode of claim 38 wherein said light enhancement features comprise a combination of at least two of shaped surfaces, textured surfaces, and reflectors.

43. A light emitting diode comprising:

a substrate;

an active region formed on said substrate, wherein said active region comprises at least one n-type layer and one p-type layer;

said substrate and said active region defining a plurality of exterior surfaces;

one of said exterior surfaces having a light enhancement feature selected from the group consisting of shaping and texturing;

the remainder of said exterior surfaces having light enhancement features selected from the group consisting of shaping, texturing, and reflectors;

ohmic contacts in a lateral orientation on a first surface of said active region, each of said ohmic contacts on a respective one of the exterior surfaces having a light enhancement feature;

wherein at least one light enhancement feature on one of said exterior surfaces is a shaped beveled cut in which said exterior surface defines a non-perpendicular angle with respect to said active region; and

wherein at least one of said exterior surfaces is below said substrate.

44. A light emitting diode according to claim 43 wherein at least one exterior surface includes a reflector.