High reflectivity p-contacts for group lll-nitride light emitting diodes

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.

1 . A flip-chip LED device comprising: 
 a plurality of group III-nitride semiconductor layers defining a p/n junction and including a top p-type group III-nitride layer; and    a p-contact for flip-chip bonding the top p-type group III-nitride layer, the p-contact including:    an aluminum layer disposed on the top p-type group III-nitride layer, and    an interface layer disposed between the aluminum layer and the top p-type group III-nitride layer and reducing a contact resistance therebetween, the interface layer comprising one or more group III-nitride layers.    
   
   
       2 . The flip-chip LED device as set forth in  claim 1 , wherein the p-contact further comprises: 
 a bonding stack including at least one layer disposed adjacent to the aluminum layer, the bonding stack being adapted for flip-chip bonding the flip-chip LED device to an associated bonding pad.    
   
   
       3 . The flip-chip LED device as set forth in  claim 1 , wherein the interface layer of the p-contact is formed by a process comprising: 
 exposing the top p-type group III-nitride layer to hydrochloric acid; and    subsequent to the exposing to hydrochloric acid, exposing the top p-type group III-nitride layer to a piranha solution.    
   
   
       4 . The flip-chip LED device as set forth in  claim 1 , wherein the top p-type group III-nitride layer is a p-GaN layer, and the interface layer of the p-contact comprises: 
 a p-InGaN layer.    
   
   
       5 . The flip-chip LED device as set forth in  claim 1 , wherein the interface layer of the p-contact comprises: 
 a tunnel junction.    
   
   
       6 . The flip-chip LED device as set forth in  claim 5 , wherein the interface layer of the p-contact further comprises: 
 an n-type group III-nitride layer disposed between the tunnel junction and the aluminum layer of the p-contact.    
   
   
       7 . The flip-chip LED device as set forth in  claim 1 , wherein the interface layer of the p-contact comprises: 
 a degenerately doped p-type group III-nitride layer adjacent the top p-type group III-nitride layer; and    a degenerately doped n-type group III-nitride layer adjacent the degenerately doped p-type group III-nitride layer.    
   
   
       8 . The flip-chip LED device as set forth in  claim 7 , wherein the interface layer of the p-contact further comprises: 
 an n-type group III-nitride layer adjacent the degenerately doped n-type group III-nitride layer.