High Efficiency Group III Nitride LED with Lenticular Surface

• US 20090242918A1
• Filed: 03/11/2009
• Published: 10/01/2009
• 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, Donofrio, Matthew, Slater, David Beardsley JR., Bharathan, Jayesh
• Granted Patent: US 8,183,588 B2
• Time in Patent Office: Days
• 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; and

a p-type gallium nitride epitaxial layer adjacent said encapsulated mirror;

2. A light emitting diode according to claim 1 further comprising:

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.

16. A light emitting diode according to claim 1 having a lenticular surface on said mirror.

17. A light emitting diode comprising

a substrate;

a Group III nitride LED structure on said substrate that includes an n-type layer and a p-type layer;

said substrate including at least one surface that is oblique to the plane of said Group III nitride LED structure;

a transparent conductive oxide on said p-type layer;

a bond pad on said transparent conductive oxide; and

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

18. A light emitting diode according to claim 17 wherein said substrate is selected from the group consisting of silicon, silicon carbide, and sapphire.

19. A light emitting diode according to claim 17 wherein said transparent conductive oxide comprises indium tin oxide.

20. A light emitting diode according to claim 17 wherein said bond pad to said n-type gallium nitride layer includes an ohmic contact.

21. A light emitting diode according to claim 17 further comprising a phosphor-containing structure adjacent said p-type gallium nitride layer for converting emissions from said light emitting region into frequencies that will produce white light

22. A light emitting diode according to claim 17 wherein said substrate comprises single crystal silicon carbide and said silicon carbide has a polytype selected from the 3C, 4H, 6H and 15R polytypes of silicon carbide.