Light emitting diodes having group III nitride surface features defined by a mask and crystal planes

• US 8,896,008 B2
• Filed: 04/23/2013
• Issued: 11/25/2014
• Est. Priority Date: 04/23/2013
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew
• Primary Examiner(s): YUSHIN, NIKOLAY K
• Application Number:
  US13/868,361
• Publication Number:
  US 20140312373A1
• Time in Patent Office: 581 Days
• Field of Search: 257/98, 257/99, 257/79
• US Class Current: 257/98
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• 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 33/32 containing nitrogen
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

An LED includes a mesa having a Group III Nitride mesa face and a mesa sidewall, on an underlying LED structure. The mesa face includes Group III Nitride surface features having tops that are defined by mask features, having bottoms, and having sides that extend along crystal planes of the Group III Nitride. The mask features may include a two-dimensional array of dots that are spaced apart from one another. Related fabrication methods are also disclosed.

Claims

1. Light Emitting Diode (LED) comprising:

a mesa that comprises a Group III Nitride mesa face and a mesa sidewall, on an underlying LED structure;

an array of Group III Nitride truncated cones in the mesa face, at least two adjacent truncated cones in the array being spaced apart from one another; and

a plurality of non-truncated cones between the at least two adjacent truncated cones that are spaced apart from one another.

2. An LED according to claim 1 wherein the Group III Nitride truncated cones comprise elliptical, circular and/or polygonal bases.

3. An LED according to claim 2 wherein the elliptical, circular and/or polygonal bases of at least two adjacent truncated cones touch one another.

4. An LED according to claim 3 wherein the bases of the adjacent truncated cones that touch one another form a hexagonal closest-packed structure.

5. An LED according to claim 1 wherein the non-truncated cones between the adjacent truncated cones are shorter than the adjacent truncated cones.

6. An LED according to claim 1 wherein the mesa is textured between at least two the adjacent truncated cones that are spaced apart from one another.

7. An LED according to claim 1 further comprising a transparent feature on exposed bases of the Group III Nitride truncated cones.

8. An LED according to claim 1 wherein exposed bases of the Group III Nitride truncated cones are textured.

9. An LED according to claim 1 wherein the Group III Nitride truncated cones have sides that extend along crystal planes of the Group III Nitride.

10. A Light Emitting Diode (LED) comprising:

a mesa that comprises a Group III Nitride mesa face and a mesa sidewall, on an underlying LED structure;

the mesa face comprising therein a plurality of Group III Nitride surface features comprising tops defined by mask features, comprising bottoms, and comprising sides that extend between the tops and the bottoms along crystal planes of the Group III Nitride.

11. An LED according to claim 10 wherein the mask features comprise a two-dimensional array of dots that are spaced apart from one another.

12. An LED according to claim 11 wherein the dots comprise elliptical, circular and/or polygonal dots.

13. An LED according to claim 11 wherein a size and/or pitch of the dots are configured so that at least some of the Group III Nitride surface features touch one another.

14. An LED according to claim 11 wherein a size and/or pitch of the dots are configured so that at least some of the Group III Nitride surface features are spaced apart from one another.

15. An LED according to claim 10 wherein the Group III Nitride surface features are produced using a wet chemical etch through the mask features.

16. An LED according to claim 10 wherein the bottoms of the plurality of Group III Nitride surface features cover at least about 35% of an area of the Group III Nitride mesa face.

17. An LED according to claim 10 wherein the bottoms of the plurality of Group III Nitride surface features cover at least about 50% of an area of the Group III Nitride mesa face.

18. An LED according to claim 10 wherein the bottoms of the plurality of Group III Nitride surface features cover at least about 90% of an area of the Group III Nitride mesa face.

19. An LED according to claim 10 wherein an aspect ratio of a height of the Group III Nitride surface features to the bottoms of the Group III Nitride surface features is at least about 0.2.

20. An LED according to claim 10 wherein an aspect ratio of a height of the Group III Nitride surface features to the bottoms of the Group III Nitride surface features is at least about 0.3.

21. An LED according to claim 16 wherein an aspect ratio of a height of the Group III Nitride surface features to the bottoms of the Group III Nitride surface features is at least about 0.4.

22. An LED according to claim 10 wherein a height of the Group III Nitride surface features is less than about 50% of a thickness of a Group III Nitride layer that is included in the mesa.

23. An LED according to claim 10 wherein an angle between the side and bottom of the Group III Nitride surface features is between about 45°

and about 75°

.

24. An LED according to claim 16 wherein an angle between the side and the bottom of the Group III Nitride surface features is about 62°

.

25. An LED according to claim 10 wherein the bottoms of the Group III Nitride surface features touch one another and wherein a height of the Group III Nitride surface features exceeds about 1 μ

M.

26. An LED according to claim 16 wherein the bottoms of the Group III Nitride surface features touch one another and wherein a height of the Group III Nitride surface features exceeds about 1 μ

m.

27. An LED according to claim 10 wherein the mesa comprises a Group III Nitride layer that is at least about 1 μ

m thick beneath the bottoms of the plurality of Group III Nitride surface features.

28. An LED according to claim 10 wherein the mesa comprises a Group III Nitride layer that is at least about 2 μ

m thick beneath the bottoms of the plurality of Group III Nitride surface features.