Semiconductor light emitting device

Abstract

A semiconductor light emitting device includes a first semiconductor layer, an active layer disposed on the first semiconductor layer to emit ultraviolet light, a second semiconductor layer disposed on the active layer, and a first electrode disposed on the first semiconductor layer and being in Ohmic contact with a portion of the first semiconductor layer, the first electrode including a contact electrode including aluminum (Al) and at least one other material and having a first region adjacent to the first semiconductor layer and a second region, with each region having an Al composition ratio defined by the amount of Al relative to the amount of the at least one other material, wherein the Al composition ratio of the first region is greater than the Al composition ratio of the second region, and a metal layer disposed on the contact electrode.

What is claimed is: 
     
         1 . A semiconductor light emitting device comprising:
 a first semiconductor layer;   an active layer disposed on the first semiconductor layer to emit ultraviolet light;   a second semiconductor layer disposed on the active layer; and   a first electrode disposed on the first semiconductor layer and being in Ohmic contact with a portion of the first semiconductor layer, the first electrode comprising:
 a contact electrode comprising aluminum (Al) and at least one other material and having a first region adjacent to the first semiconductor layer and a second region, with each region having an Al composition ratio defined by the amount of Al relative to the amount of the at least one other material, wherein the Al composition ratio of the first region is greater than the Al composition ratio of the second region; and 
 a metal layer disposed on the contact electrode. 
   
     
     
         2 . The device of  claim 1 , wherein the first region comprises a bottom surface and the second region comprises a top surface of the contact electrode. 
     
     
         3 . The device of  claim 2 , wherein at least one of the first region and the second region has a thickness of about one half of the total thickness of the contact electrode. 
     
     
         4 . The device of  claim 1 , wherein the contact electrode comprises at least one material selected from the group consisting of Cr, Ti, Al, Au, and combinations thereof, or an alloy of the material. 
     
     
         5 . The device of  claim 1 , wherein at least one of the first semiconductor layer and the active layer comprises Al. 
     
     
         6 . The device of  claim 1 , wherein the metal layer comprises:
 a reflective layer to reflect light; and   a barrier layer disposed on the reflective layer to prevent diffusion of metal atoms or metal ions from the reflective layer.   
     
     
         7 . The device of  claim 6 , wherein:
 the reflective layer comprises at least one of Al, Al alloy, Ag, and Ag alloy, and   the barrier layer comprises at least one of W, TiW, Mo, Ti, Cr, Pt, Rh, Pd, and Ni.   
     
     
         8 . The device of  claim 1 , wherein a contact resistance between the first semiconductor layer and the contact electrode is different from a contact resistance between the first semiconductor layer and the metal layer. 
     
     
         9 . The device of  claim 1 , further comprising a second electrode being in Ohmic contact with the second semiconductor layer. 
     
     
         10 . The device of  claim 9 , further comprising:
 a first pad electrically connected to the first electrode and disposed on the first electrode; and   a second pad electrically connected to the second electrode and disposed on the second electrode.   
     
     
         11 . The device of  claim 9 , further comprising:
 a first bump electrically connected to the first electrode and disposed on the first electrode; and   a second bump electrically connected to the second electrode and disposed on the second electrode.   
     
     
         12 . The device of  claim 10 , further comprising an insulating layer disposed on the first pad and the second pad such that at least a part of the first pad and the second pad are exposed. 
     
     
         13 . The device of  claim 12 , further comprising:
 a first bump electrically connected to the first electrode and disposed on the first electrode; and   a second bump electrically connected to the second electrode and disposed on the second electrode.   
     
     
         14 . A semiconductor light emitting device comprising:
 a first semiconductor layer;   an active layer disposed on the first semiconductor layer to emit ultraviolet light;   a second semiconductor layer disposed on the active layer; and   a first electrode disposed on the first semiconductor layer and including a plurality of metal layers, with one of the plurality of metal layers having a relatively planar lower surface and an irregular top surface, the lower surface being in Ohmic contact with the first semiconductor layer.   
     
     
         15 . The device of  claim 14 , wherein:
 the one metal layer comprises a contact electrode in Ohmic contact with a portion of the first semiconductor layer,   other of the plurality of the metal layers is electrically connected to the contact electrode, and   at least a part of the other metal layer is disposed on and in contact with the first semiconductor layer.   
     
     
         16 . The device of  claim 15 , wherein the contact electrode has a width shorter than a width over which the other metal layer and the first semiconductor layer are in contact with each other. 
     
     
         17 . The device of  claim 15 , wherein the other metal layer surrounds the contact electrode. 
     
     
         18 . The device of  claim 15 , wherein the other metal layer comprises:
 a reflective layer to reflect light; and   a barrier layer disposed on the reflective layer to prevent diffusion of metal atoms or metal ions from the reflective layer.   
     
     
         19 . The device of  claim 14 , further comprising a second electrode being in Ohmic contact with the second semiconductor layer. 
     
     
         20 . The device of  claim 19 , further comprising:
 a first bump electrically connected to the first electrode and disposed on the first electrode; and   a second bump electrically connected to the second electrode and disposed on the second electrode.