External extraction light emitting diode based upon crystallographic faceted surfaces

• US 8,357,923 B2
• Filed: 07/12/2010
• Issued: 01/22/2013
• Est. Priority Date: 05/18/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John A., Slater, David B. Jr., Kong, Hua Shuang, Donofrio, Matthew
• Primary Examiner(s): Picardat, Kevin M
• Application Number:
  US12/834,608
• Publication Number:
  US 20100276700A1
• Time in Patent Office: 925 Days
• Field of Search: 438/39, 438/40, 438/42, 438/43, 438/46, 438/47, 257/13, 257/79, 257/94, 257/95, 257/98, 257/103
• US Class Current: 257/13
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/105 with a resonant cavity structure
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• 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 33/38 with a particular shape
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating

Abstract

A light emitting diode is disclosed that includes a support structure and a Group III nitride light emitting active structure mesa on the support structure. The mesa has its sidewalls along an indexed crystal plane of the Group III nitride. A method of forming the diode is also disclosed that includes the steps of removing a substrate from a Group III nitride light emitting structure that includes a sub-mount structure on the Group III nitride light emitting structure opposite the substrate, and thereafter etching the surface of the Group III nitride from which the substrate has been removed with an anisotropic etch to develop crystal facets on the surface in which the facets are along an index plane of the Group III nitride. The method can also include etching the light emitting structure with an anisotropic etch to form a mesa with edges along an index plane of the Group III nitride.

Claims

1. A light emitting diode comprising a Group III nitride light emitting active structure mesa comprising sidewalls produced using a wet chemical etch.

2. A light emitting diode according to claim 1, wherein the emitting face of said diode is a Group III nitride surface of said active structure.

3. A light emitting diode according to claim 1, further compromising a support structure for said mesa, said support structure being selected from the group consisting of metals, semiconductor substrates, and sub-mount structures.

4. A light emitting diode according to claim 1, wherein said light emitting active structure comprises at least one p-type layer of gallium nitride and at least one n-type layer of gallium nitride.

5. A light emitting diode according to claim 4, wherein said gallium nitride layers terminate in an indexed crystal plane edge of said mesa sidewalls.

6. A light emitting diode according to claim 1, wherein said mesa sidewalls are along the (hkil) crystal plane of gallium nitride.

7. A light emitting diode according to claim 1, wherein said mesa sidewalls are along the {10-11} family of crystal planes of hexagonal gallium nitride.

8. A light emitting diode according to claim 1 further comprising a mirror between said light emitting active structure and said support structure.

9. A plurality of light emitting diodes according to claim 1 on a common wafer.

10. A light emitting diode according to claim 1 further comprising a roughened surface formed of a plurality of crystallographic features that demonstrate indexed planes of the Group III nitride.

11. A light emitting diode according to claim 10, wherein said indexed planes of said roughened surface are congruent with an indexed crystal plane of said mesa sidewall.

12. A light emitting diode according to claim 3, comprising an ohmic contact to said support structure and an ohmic contact to said active structure.

13. A light emitting diode according to claim 10 comprising an ohmic contact to said roughened surface.

14. A light emitting diode according to claim 3, wherein said sidewalls form an angle of between approximately 58 and 62 degrees with respect to said support structure.

15. A light emitting diode according to claim 1, wherein said chemically developed sidewalls have been treated by an anisotropic wet etch.

16. A light emitting diode according to claim 15, wherein said anisotropic wet etch is from a group which includes potassium hydroxide, sodium hydroxide, potassium hexacyanoferrate, and combinations thereof.

17. A light emitting diode according to claim 1 further comprising said Group III nitride light emitting active structure mesa having a chemically developed surface.

18. A light emitting diode according to claim 17, further comprising at least a portion of said chemically developed surface dry etched.