Light-emitting device

Abstract

A light-emitting device includes a first semiconductor layer; a plurality of semiconductor pillars separated from each other and formed on the first semiconductor layer, the plurality of semiconductor pillars respectively includes a second semiconductor layer and an active layer; a first electrode covering one portion of the plurality of semiconductor pillars; and a second electrode covering another portion of the plurality of semiconductor pillars, wherein the plurality of semiconductor pillars under a covering region of the first electrode are separated from each other by a first space, the plurality of semiconductor pillars outside the covering region of the first electrode are separated from each other by a second space, and the first space is larger than the second space.

What is claimed is: 
     
         1 . A light-emitting device, comprising:
 a substrate;   an aluminum nitride (AlN) buffer layer formed on the substrate;   a first semiconductor layer comprising Al x Ga (1-x) N formed on the aluminum nitride (AlN) buffer layer, wherein x>0;   a semiconductor pillar formed on the first semiconductor layer, comprising a second semiconductor layer and an active layer;   a first contact layer formed on the first semiconductor layer, wherein the first contact layer comprises a first contact portion and a first extending portion connected to the first contact portion, wherein the first extending portion surrounds the semiconductor pillar;   a second contact layer formed on the second semiconductor layer of the semiconductor pillar;   an insulating layer formed on the first contact layer and the second contact layer, comprising a first opening exposing the first contact portion of the first contact layer and a second opening exposing the second contact layer;   a first electrode covering the first opening; and   a second electrode covering the second opening.   
     
     
         2 . The light-emitting device according to  claim 1 , wherein 0.3<x<0.8. 
     
     
         3 . The light-emitting device according to  claim 1 , wherein 0.35<x<0.7. 
     
     
         4 . The light-emitting device according to  claim 1 , wherein 0.4<x<0.6. 
     
     
         5 . The light-emitting device according to  claim 1 , wherein the first contact layer and the second contact layer do not overlap each other. 
     
     
         6 . The light-emitting device according to  claim 1 , wherein the first contact layer comprises a plurality of first contact portions and a plurality of first extending portions connected to each other. 
     
     
         7 . The light-emitting device according to  claim 1 , wherein the first semiconductor layer comprising Al x Ga (1-x) N is formed on a flat surface of the substrate. 
     
     
         8 . The light-emitting device according to  claim 1 , wherein the first contact portion of the first contact layer comprises a width larger than a width of the first extending portion. 
     
     
         9 . The light-emitting device according to  claim 1 , wherein the first contact layer is covered by the first electrode and the second electrode. 
     
     
         10 . The light-emitting device according to  claim 1 , wherein the aluminum nitride (AlN) buffer layer comprises a thickness greater than 2500 nm. 
     
     
         11 . The light-emitting device according to  claim 1 , wherein the aluminum (Al) composition percentage of the aluminum nitride (AlN) buffer layer is greater than that of Al x Ga (1-x) N of the first semiconductor layer. 
     
     
         12 . The light-emitting device according to  claim 1 , wherein the insulating layer covers the first extending portion of the first contact layer. 
     
     
         13 . The light-emitting device according to  claim 1 , wherein the first contact layer does not comprise silver (Ag). 
     
     
         14 . The light-emitting device according to  claim 1 , wherein the first contact layer comprises one side comprising chromium (Cr) or titanium (Ti) to be in contact with the first semiconductor layer. 
     
     
         15 . The light-emitting device according to  claim 1 , wherein the first contact layer comprises titanium (Ti) and aluminum (Al). 
     
     
         16 . The light-emitting device according to  claim 15 , wherein a ratio of a titanium (Ti) layer to an aluminum (Al) layer is between 0.1 and 0.2. 
     
     
         17 . The light-emitting device according to  claim 1 , wherein the active layer comprises one or more well layers and one or more barrier layers alternatively stacked, wherein the well layer comprises Al x Ga 1-x N and 0.2<x<0.4, and the barrier layer comprises Al y Ga 1-y N and 0.4<y<0.7. 
     
     
         18 . The light-emitting device according to  claim 1 , wherein an UV light comprising a wavelength shorter than 370 nm is emitted from the light-emitting device. 
     
     
         19 . The light-emitting device according to  claim 1 , wherein the insulating layer comprises two or more layers having different refractive indexes alternately stacked to form a Distributed Bragg reflector (DBR). 
     
     
         20 . The light-emitting device according to  claim 1 , wherein the second contact layers comprises a transparent conductive material.