High efficiency group III nitride LED with lenticular surface

• US 8,183,588 B2
• Filed: 03/11/2009
• Issued: 05/22/2012
• 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:
  US12/401,843
• Publication Number:
  US 20090242918A1
• Time in Patent Office: 1,168 Days
• Field of Search: 257/98, 257/103, 257/E33.034, 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 that includes a conductive substrate, a bonding metal on the conductive substrate and a barrier metal layer on the bonding metal. A mirror layer is encapsulated by the barrier metal layer and is isolated from the bonding metal by the barrier layer. A p-type gallium nitride epitaxial layer is on the encapsulated mirror, an indium gallium nitride active layer is on the p-type layer, and an n-type gallium nitride layer is on the indium gallium nitride layer, and a bond pad is made to the n-type gallium nitride layer.

Claims

1. A light emitting diode comprising:

a submount structure;

a bonding metal on said submount structure;

a barrier metal layer on said bonding metal;

an ohmic mirror layer encapsulated by said barrier metal layer;

an epitaxial light emitting region on said encapsulated mirror; and

a lenticular surface at least partially on said epitaxial light emitting region wherein said lenticular surface comprises silicon carbide.

2. A light emitting diode according to claim 1, said epitaxial light emitting region comprising:

a p-type gallium nitride epitaxial layer;

an indium gallium nitride active layer on said p-type layer;

an n-type gallium nitride layer on said indium gallium nitride layer; and

a bond pad to said n-type gallium nitride layer.

3. A light emitting diode according to claim 1 wherein said ohmic mirror layer comprises a reflective metal layer and an ohmic metal layer.

4. A light emitting diode according to claim 3 wherein said reflective metal layer includes silver and said ohmic metal layer includes platinum.

5. A light emitting diode according to claim 1 comprising a plurality of barrier metal layers on said bonding metal.

6. A light emitting diode according to claim 2 wherein said barrier metal layer is selected from the group consisting of titanium, tungsten, tin and combinations and alloys of these metals.

7. A light emitting diode according to claim 1 wherein said active layer is in a mesa that includes a passivation layer that covers otherwise exposed portions of said mirror, said barrier metal and said bonding metal layer.

8. A light emitting diode according to claim 7 wherein said passivation layer is selected from the group consisting of stoichiometric silicon nitride, non-stoichiometric silicon nitride, and silicon dioxide.

9. A light emitting diode according to claim 1 wherein said bonding metal layer is selected from the group consisting of gold, tin and eutectic mixtures of gold and tin.

10. A light emitting diode according to claim 1 wherein said submount is selected from the group consisting of silicon, silicon carbide, gallium arsenide and copper tungsten.

11. A light emitting diode according to claim 2 wherein said bond pad includes an ohmic contact to said n-type gallium nitride layer.

12. A light emitting diode according to claim 1 further comprising an ohmic contact to said submount.

13. A light emitting diode according to claim 12 having a total dimension between and including said ohmic contacts of no more than 150 microns.

14. A light emitting diode according to claim 1 further comprising a phosphor-containing structure adjacent said n-type gallium nitride layer for converting emissions from said light emitting region into frequencies that will produce white light.

15. A light emitting diode according to claim 10 wherein said submount comprises single crystal silicon carbide and said silicon carbide has a polytype selected from the 3C, 4H, 6H and 15R polytypes of silicon carbide.