Methods for forming aluminum-containing p-contacts for group III-nitride light emitting diodes
View Patent ↗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.
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.