Light emitting diode with improved luminous efficiency

Abstract

A light-emitting diode includes a substrate, and a light-emitting structure disposed on the substrate. The light-emitting structure includes a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer. A transparent electrode layer including concave portions and convex portions is disposed on the second conductivity-type semiconductor layer. Micro-lenses are disposed on the transparent electrode layer and completely cover the concave portions, and only partially cover the convex portions that are disposed between the micro-lenses.

What is claimed is: 
     
         1 . A light-emitting diode, comprising:
 a substrate;   a light-emitting structure disposed on the substrate, the light-emitting structure comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;   a transparent electrode layer disposed on the second conductivity-type semiconductor layer, the transparent electrode comprising an upper surface comprising concave portions and convex portions; and   micro-lenses disposed on the transparent electrode layer and completely covering the concave portions, and only partially covering the convex portions that are disposed between the micro-lenses.   
     
     
         2 . The light-emitting diode of  claim 1 , wherein the transparent electrode layer concave portions comprise blind holes having a depth less than a thickness of the transparent electrode layer. 
     
     
         3 . The light-emitting diode of  claim 1 , wherein the transparent electrode layer concave portions comprise through-holes in the transparent electrode layer. 
     
     
         4 . The light-emitting diode of  claim 1 , wherein the micro-lenses comprise a material having a lower refractive index than the transparent electrode layer. 
     
     
         5 . The light-emitting diode of  claim 4 , wherein the micro-lenses comprise SiO 2 . 
     
     
         6 . The light-emitting diode of  claim 4 , wherein the second conductivity-type semiconductor layer comprises a GaN-based semiconductor layer, the transparent electrode layer comprises an indium tin oxide (ITO) layer, and the micro-lenses comprise SiO 2 . 
     
     
         7 . The light-emitting diode of  claim 1 , wherein the micro-lenses comprise a vertical cross-section comprising a width that decreases in a direction extending away from the substrate. 
     
     
         8 . The light-emitting diode of  claim 1 , wherein the micro-lenses comprise a vertical cross-section comprising at least two inclined surfaces having an obtuse angle defined therebetween. 
     
     
         9 . The light-emitting diode of  claim 1 , wherein the micro-lenses comprise a horizontal cross-section having a circular shape, an elliptical shape, a hexagonal shape, a rectangular shape, or a triangular shape. 
     
     
         10 . A method of fabricating a light-emitting diode (LED), the method comprising:
 forming epitaxial layers on a substrate, the epitaxial layers comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;   etching the epitaxial layers to expose the first conductivity-type semiconductor layer;   forming a transparent electrode layer on the epitaxial layers;   etching the transparent electrode layer to form concave portions and convex portions; and   forming micro-lenses comprising a transparent material on the transparent electrode layer, the micro-lenses completely covering the concave portions and only partially covering the convex portions.   
     
     
         11 . The method of  claim 10 , wherein etching the transparent electrode layer comprises forming blind holes. 
     
     
         12 . The method of  claim 10 , wherein etching the transparent electrode layer comprises exposing the second conductivity-type semiconductor layer to form through-holes. 
     
     
         13 . The method of  claim 10 , wherein forming the micro-lenses comprises:
 forming a transparent insulation layer covering the transparent electrode layer; and   etching the transparent insulation layer to form the micro-lenses at positions corresponding to the concave portions.