Multi-layer highly reflective ohmic contacts for semiconductor devices

• US 6,992,334 B1
• Filed: 12/22/1999
• Issued: 01/31/2006
• Est. Priority Date: 12/22/1999
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Krames, Michael R, Wierer, Jonathan J. Jr., Rudaz, Serge L
• Primary Examiner(s): JACKSON JR, JEROME
• Application Number:
  US09/469,652
• Time in Patent Office: 2,232 Days
• Field of Search: 257/77, 257/741, 257/96, 257/98, 257/99, 257/700, 257742-745, 257/766, 257/762
• US Class Current: 257/98
• CPC Class Codes: H01L 33/405 Reflective materials

Abstract

A high performance, highly reflective ohmic contact, in the visible spectrum (400 nm–750 nm), has the following multi-layer metal profile. A uniform and thin ohmic contact material is deposited and optionally alloyed to the semiconductor surface. A thick reflector layer selected from a group that includes Al, Cu, Au, Rh, Pd, Ag and any multi-layer combinations is deposited over the ohmic contact material.

Claims

1. A light-emitting semiconductor device comprising:

a semiconductor structure having at least one p-type and one n-type layer; and

a p contact and an n contact, the p contact electrically connected to the p-type layer, the n contact electrically connected to the n-type layer, wherein at least one of the p and n contacts is a multi-layer contact external to the semiconductor structure, the multi-layer contact comprising;

a metallic reflector layer comprising Ag; and

a continuous uniform conducting sheet adjacent to the semiconductor structure, wherein the continuous uniform conducting sheet comprises Ni and makes ohmic contact to the structure;

wherein the multi-layer contact has a reflectivity greater than 75% for light at an operating wavelength of the light-emitting device and a specific contact resistance less than 10<sup>−

2</sup> Ω

-cm².

2. A device, as defined in claim 1, the multi-layer contact further comprising a barrier layer interposing the reflector layer and the continuous uniform conducting sheet.

3. A device, as defined in claim 1, the reflector layer having a thickness greater than 500 Å

.

4. A device, as defined in claim 1, wherein the continuous uniform conducting sheet has a thickness less than 200 Å

.

5. A device, as defined in claim 1, wherein the continuous uniform conducting sheet is selected from the group that consists of Au/NiO and Ni/Au.

6. A device, as defined in claim 1, wherein the semiconductor structure includes at least one III-nitride layer.

7. A device, as defined in claim 1, wherein the continuous uniform conducting sheet absorbs less than 25% of light generated in the semiconductor structure and incident on the continuous uniform conducting sheet.

8. A device, as defined in claim 6, wherein a voltage required to forward bias the device is less than 3.5 V.

9. A device, as defined in claim 1, wherein the continuous uniform conducting sheet has thickness less than 100 Å

.

10. A light-emitting semiconductor device comprising:

a semiconductor structure having at least one p-type and one n-type layer; and

a p contact and an n contact, the p contact electrically connected to the p-type layer, the n contact electrically connected to the n-type layer, wherein at least one of the p and n contacts is a multi-layer contact external to the semiconductor structure, the multi-layer contact comprising;

a metallic reflector comprising Al; and

a continuous uniform conducting sheet adjacent to the semiconductor structure, wherein the continuous uniform conducting sheet comprises Ni and makes ohmic contact to the structure;

wherein the multi-layer contact has a reflectivity greater than 75% for light at an operating wavelength of the light-emitting device and a specific contact resistance less than 10<sup>−

2</sup> Ω

-cm².

11. A device, as defined in claim 10, wherein:

the continuous uniform conducting sheet comprises Au.