Light emitting devices having roughened/reflective contacts and methods of fabricating same

• US 8,669,563 B2
• Filed: 06/02/2009
• Issued: 03/11/2014
• Est. Priority Date: 07/27/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Haberern, Kevin, Bergmann, Michael John, Mieczkowski, Van, Emerson, David Todd
• Primary Examiner(s): SEFER, AHMED N
• Application Number:
  US12/476,519
• Publication Number:
  US 20090250716A1
• Time in Patent Office: 1,743 Days
• Field of Search: 257/79, 257/98, 257/99, 438/29
• US Class Current: 257/79
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/12036 PN diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

Light emitting devices include an active region of semiconductor material and a first contact on the active region. The first contact is configured such that photons emitted by the active region pass through the first contact. A photon absorbing wire bond pad is provided on the first contact. The wire bond pad has an area less than the area of the first contact. A reflective structure is disposed between the first contact and the wire bond pad such that the reflective structure has substantially the same area as the wire bond pad. A second contact is provided opposite the active region from the first contact. The reflective structure may be disposed only between the first contact and the wire bond pad. Methods of fabricating such devices are also provided.

Claims

1. A light emitting device, comprising:

an active region;

a contact layer on the active region, the contact layer including a roughened area and a non-roughened area outside the roughened area;

a reflective metal layer comprising silver and/or aluminum directly on the roughened area of the contact layer; and

a photon absorbing bond pad on the reflective metal layer, the photon absorbing bond pad being adjacent the roughened area and remote from the non-roughened area.

2. The light emitting device of claim 1, further comprising a p-type semiconductor material disposed between the contact layer and the active region.

3. The light emitting device of claim 1, wherein the active region comprises a Group III-nitride based active region.

4. A light emitting device, comprising:

an active region;

a semiconductor material on the active region;

a contact layer on the semiconductor material opposite the active region;

a photon absorbing bond pad on a first portion of the contact layer and exposing a second portion of the contact layer; and

a roughened reflective structure disposed between the contact layer and the bond pad and that does not extend beyond the bond pad to the second portion of the contact layer, wherein the bond pad also does not extend onto a sidewall of the roughened reflective structure, the roughened reflective structure comprising a roughened layer of silver and/or aluminum that is configured to reflect photons incident in a region of the photon absorbing bond pad, so as to reduce an amount of photons absorbed by the photon absorbing bond pad.

5. The light emitting device of claim 4, wherein the roughened reflective structure has substantially the same area as the bond pad.

6. The light emitting device of claim 4, wherein the roughened reflective structure is substantially congruent with the bond pad.

7. The light emitting device of claim 4, wherein the semiconductor material is a p-type semiconductor material.

8. The light emitting device of claim 4, wherein the active region comprises a Group III-nitride based active region.

9. The light emitting device of claim 4, wherein the reflective structure is self-aligned with the bond pad.

10. A method of fabricating a light emitting device, comprising:

forming a contact layer on an active region; and

forming a reflective structure on the contact layer, wherein forming the reflective structure comprises;

roughening an area of the contact layer;

forming a mask layer on the contact layer, the mask layer having an opening that exposes at least some of the area of the contact layer that was roughened;

depositing a metal layer comprising silver and/or aluminum in the opening of the mask layer directly on the area of the contact layer that was roughened; and

depositing a photon absorbing bond pad on the metal layer in the opening of the mask.

11. The method of claim 10, further comprising forming a p-type semiconductor material disposed between the contact layer and the active region.

12. The method of claim 10, wherein forming a contact layer on an active region is preceded by forming a Group III-nitride based active region.

13. A method of fabricating a light emitting device, comprising:

forming a contact layer on an active region;

forming a mask layer on the contact layer, the mask layer having an opening that exposes a portion of the contact layer;

roughening at least some of the portion of the contact layer exposed by the opening of the mask layer;

depositing a metal layer comprising silver and/or aluminum directly on the portion of the contact layer that was roughened; and

depositing a photon absorbing bond pad on the metal layer in the opening of the mask layer.

14. The method of claim 13, further comprising forming a p-type semiconductor material disposed between the contact layer and the active region.

15. The method of claim 13, wherein forming a contact layer on an active region is preceded by forming a Group III-nitride based active region.

16. A method of fabricating a light emitting device, comprising:

forming a contact layer on an active region;

forming a roughened area of the contact layer, the roughened area defining a non-roughened area of the contact layer outside the roughened area;

forming a metal layer comprising silver and/or aluminum directly on the roughened area of the contact layer; and

depositing a photon absorbing bond pad on the metal layer, adjacent the roughened area and remote from the non-roughened area.

17. The method of claim 16, further comprising forming a p-type semiconductor material disposed between the contact layer and the active region.

18. The method of claim 16, wherein forming a contact layer on an active region is preceded by forming a Group III-nitride based active region.