Methods for forming aluminum-containing p-contacts for group III-nitride light emitting diodes

• US 7,022,550 B2
• Filed: 04/07/2004
• Issued: 04/04/2006
• Est. Priority Date: 04/07/2004
• Status: Active Grant

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: Gelcore (General Electric Company)
• Inventors: Venugopalan, Hari S.
• Primary Examiner(s): Huynh, Andy
• Application Number:
  US10/819,740
• Publication Number:
  US 20050224990A1
• Time in Patent Office: 727 Days
• Field of Search: None
• US Class Current: 438/108
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/0508 being stacked
• CPC Class Codes: H01L 2224/05124 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05155 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05166 Titanium [Ti] as principal constituent
• CPC Class Codes: H01L 2224/05169 Platinum [Pt] as principal constituent
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/05655 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05666 Titanium [Ti] as principal constituent
• CPC Class Codes: H01L 2224/05669 Platinum [Pt] as principal constituent
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• CPC Class Codes: H01L 2224/06102 the bonding areas being at different heights
• CPC Class Codes: H01L 2224/14 of a plurality of bump connectors
• CPC Class Codes: H01L 2224/1703 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 24/03 Manufacturing methods
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2933/0016 : relating to electrodes
• CPC Class Codes: H01L 33/20 : with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 : containing nitrogen
• CPC Class Codes: H01L 33/38 : with a particular shape
• CPC Class Codes: H01L 33/405 : Reflective materials

Abstract

A flip-chip LED device (10) includes a plurality of group III-nitride semiconductor layers (22) defining a p/n junction and including a top p-type group III-nitride layer (28), and a p-contact (30, 30′, 30″) for flip-chip bonding the top p-type group III-nitride layer. The p-contact includes an aluminum layer (32) disposed on the top p-type group III-nitride layer (28), and an interface layer (40, 66, 72, 80) disposed between the aluminum layer and the top p-type group III-nitride layer. The interface layer reduces a contact resistance between the aluminum layer (32) and the top p-type group III-nitride layer (28). The interface layer comprises one or more group III-nitride layers.

Claims

1. A method for forming a p-contact on a top p-type group III-nitride layer of a flip-chip LED device, the method comprising:

forming an interface layer including a tunnel junction on the top p-type group III-nitride layer; and

forming an aluminum layer on the interface layer;

wherein the interface layer reduces a contact resistance between the aluminum layer and the top p-type group III-nitride layer.

2. The method as set forth in claim 1, wherein the forming of an interface layer including a tunnel junction comprises:

forming a degenerately doped p-type group III-nitride layer; and

forming a degenerately doped n-type group III-nitride layer on the degenerately doped p-type group III-nitride layer.

3. The method as set forth in claim 2, wherein the forming of an interface layer further comprises:

forming a non-degenerately doped n-type group III-nitride layer on the degenerately doped n-type group III-nitride layer.

4. The method as set forth in claim 2, wherein:

the degenerately doped p-type group III-nitride layer is selected from a group consisting of;

(i) a degenerately doped p-type InGaN layer, and (ii) a degenerately doped p-GaN layer; and

the degenerately doped n-type group III-nitride layer is selected from a group consisting of;

(i) a degenerately doped n-type InGaN layer, and (ii) a degenerately doped n-GaN layer.

5. The method as set forth in claim 1, wherein the forming of an interface layer including a tunnel junction comprises:

forming a degenerately doped p-type InGaN layer; and

forming a degenerately doped n-type InGaN layer on the degenerately doped p-type InGaN layer.

6. A method for forming a p-contact on a top p-type group III-nitride layer of a flip-chip LED device, the method comprising:

forming a p-InGaN interface layer on the top p-type group III-nitride layer; and

forming an aluminum layer on the p-InGaN interface layer;

wherein the p-InGaN interface layer reduces a contact resistance between the aluminum layer and the top p-type group III-nitride layer.

7. The method as set forth in claim 6, further comprising:

forming one or more electrically conductive layers on top of the aluminum layer, said one or more electrically conductive layers providing one of (i) a solderable surface for flip-chip soldering, and (ii) a surface for thermocompression bonding or thermosonic bonding, the p-contact to an associated mount.

8. The method as set forth in claim 6, further comprising:

exposing the formed p-InGaN interface layer to hydrochloric acid; and

subsequent to the exposing to hydrochloric acid, exposing the formed p-InGaN interface layer to a piranha solution.

9. The method as set forth in claim 8, wherein the exposing to a piranha solution comprises:

exposing the formed p-InGaN interface layer to a solution including sulfuric acid and hydrogen peroxide wherein a ratio of the sulfuric acid to the hydrogen peroxide is about 10;

1.

10. A method for forming a p-contact on a top p-type group III-nitride layer of a flip-chip LED device, the method comprising:

exposing the top p-type group III-nitride layer to hydrochloric acid;

subsequent to the exposing to hydrochloric acid, exposing the top p-type group III-nitride layer to a piranha solution including sulfuric acid and hydrogen peroxide wherein a ratio of the sulfuric acid to the hydrogen peroxide in the solution is about 10;

1; and

subsequent to the exposing to the piranha solution, disposing an aluminum layer on the top p-type group III-nitride layer.

11. The method as set forth in claim 10, further comprising:

prior to the exposing to hydrochloric acid, disposing a p-InGaN layer on the top p-type group III-nitride layer, the exposing processes and the depositing of the aluminum layer being applied to the p-InGaN layer.

12. The method as set forth in claim 10, further comprising:

prior to the exposing to hydrochloric acid, disposing a tunnel junction on the top p-type group III-nitride layer.

13. The method as set forth in claim 10, wherein the solution further includes water.

14. The method as set forth in claim 10, further comprising:

forming one or more electrically conductive layers on top of the aluminum layer, said one or more electrically conductive layers providing one of (i) a solderable surface for flip-chip soldering, and (ii) a surface for thermocompression bonding or thermosonic bonding, the p-contact to an associated mount.