High efficiency group III nitride LED with lenticular surface

• US 8,154,039 B2
• Filed: 03/11/2009
• Issued: 04/10/2012
• 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., Bharathan, Jayesh, Donofrio, Matthew
• Primary Examiner(s): Wilson, Allan R
• Application Number:
  US12/401,832
• Publication Number:
  US 20090166659A1
• Time in Patent Office: 1,126 Days
• Field of Search: 257/98, 257/E33.068
• US Class Current: 257/98
• 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 light emitting diode is disclosed having a vertical orientation with an ohmic contact on portions of a top surface of the diode and a mirror layer adjacent the light emitting region of the diode. The diode includes an opening in the mirror layer beneath the geometric projection of the top ohmic contact through the diode that defines a non-contact area between the mirror layer and the light emitting region of the diode to encourage current flow to take place other than at the non-contact area to in turn decrease the number of light emitting recombinations beneath the ohmic contact and increase the number of light emitting recombinations in the more transparent portions of the diode.

Claims

1. In a light emitting diode having a vertical orientation with a top ohmic contact on portions of a top surface of said diode and a mirror layer adjacent the light emitting region of said diode;

the improvement comprising;

an opening in said mirror layer beneath said top ohmic contact through the diode that defines a non-ohmic contact area between said mirror layer and said light emitting region of said diode to encourage current flow to take place other than at said non-ohmic contact area to in turn decrease the number of light emitting recombinations beneath said top ohmic contact and increase the number of light emitting recombinations in the more transparent portions of said diode;

wherein said opening includes a reflective metal therein that is not ohmic with respect to said light emitting region.

2. A light emitting diode according to claim 1 wherein said top ohmic contact comprises a wire bond pad having an area less than half of the area of said top surface of said diode.

3. A light emitting diode according to claim 1 formed on a substrate and having an ohmic contact to said substrate that is larger in area than said top ohmic contact.

4. A light emitting diode according to claim 3 wherein said mirror layer is positioned between said substrate and said light emitting region.

5. A light emitting diode according to claim 1 wherein the size of said non-ohmic contact area is substantially the same area as the size of said top ohmic contact.

6. A light emitting diode according to claim 1 wherein said mirror layer comprises a plurality of metal layers.

7. A light emitting diode according to claim 1 wherein said light emitting region comprises a plurality of Group III nitride layers, including at least one p-type layer and at least one n-type layer.

8. A light emitting diode according to claim 7 wherein the p-type layer of the light emitting region is on the mirror layer and the opening is adjacent to the p-type layer of the light emitting region.

9. A light emitting diode according to claim 1 wherein the mirror layer has a conductive property and a reflective property.

10. In a light emitting diode having a vertical orientation with a top ohmic contact on portions of a top surface of said diode and a mirror layer adjacent the light emitting region of said diode;

the improvement comprising;

an opening in said mirror layer beneath said top ohmic contact through the diode that defines a non-ohmic contact area between said mirror layer and said light emitting region of said diode to encourage current flow to take place other than at said non-ohmic contact area to in turn decrease the number of light emitting recombinations beneath said top ohmic contact and increase the number of light emitting recombinations in the more transparent portions of said diode;

wherein said opening is filled with a metal that is not ohmic with respect to said light emitting region to thereby provide additional reflection from said mirror layer.

11. A light emitting diode according to claim 10 wherein said top ohmic contact comprises a wire bond pad having an area less than half of the area of said top surface of said diode.

12. A light emitting diode according to claim 10 formed on a substrate and having an ohmic contact to said substrate that is larger in area than said top ohmic contact.

13. A light emitting diode according to claim 12 wherein said mirror layer is positioned between said substrate and said light emitting region.

14. A light emitting diode according to claim 10 wherein the size of said non-ohmic contact area is substantially the same area as the size of said top ohmic contact.

15. A light emitting diode according to claim 10 wherein said mirror layer comprises a plurality of metal layers.

16. A light emitting diode according to claim 10 wherein said light emitting region comprises a plurality of Group III nitride layers, including at least one p-type layer and at least one n-type layer.

17. A light emitting diode according to claim 10 wherein the light emitting region is on the mirror layer and the opening is adjacent to the light emitting region.

18. A light emitting diode according to claim 16 wherein the p-type layer of the light emitting region is on the mirror layer and the opening is adjacent to the p-type layer of the light emitting region.

19. A light emitting diode according to claim 10 wherein the mirror layer has a conductive property and a reflective property.