Light emitting diode having distributed bragg reflector

Abstract

A light-emitting diode (LED) according to an exemplary embodiment includes a light-emitting structure arranged on a first surface of a substrate, the light-emitting structure including a first conductivity-type semiconductor layer, a second conductivity-type semiconductor layer, and an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer. A first distributed Bragg reflector is arranged on a second surface of the substrate opposite to the first surface, the first distributed Bragg reflector to reflect light emitted from the light-emitting structure. The first distributed Bragg reflector has a reflectivity of at least 90% with respect to blue, green, and red light.

What is claimed is: 
     
         1 . A light-emitting diode (LED), comprising:
 a substrate comprising a pattern on a first surface thereof;   a light-emitting structure disposed on the first surface of the substrate, the light-emitting structure comprising:
 a first conductivity-type semiconductor layer; 
 a second conductivity-type semiconductor layer; and 
 an active layer disposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer; 
   a first electrode connected to the first conductivity-type semiconductor layer;   a second electrode connected to the second conductivity-type semiconductor layer;   a first distributed Bragg reflector (DBR) disposed on the light-emitting structure, wherein:
 the first and second electrodes are exposed through the first DBR; 
 the first DBR is configured to allow light in a blue wavelength range generated in the active layer to pass therethrough and to reflect light in a non-blue wavelength range; and 
   a second DBR disposed on a second surface of the substrate opposite to the first surface, wherein:
 the second DBR is configured to reflect light emitted from the light-emitting structure. 
   
     
     
         2 . The LED of  claim 1 , wherein the first and second DBRs each comprise a laminate structure comprising SiO 2  layers that are alternately stacked with TiO 2  layers or Nb 2 O 5  layers, or a combination of TiO 2  and Nb 2 O 5  layers. 
     
     
         3 . The LED of  claim 1 , wherein the second DBR comprises at least 25 pairs of SiO 2 /TiO 2  layers. 
     
     
         4 . The LED of  claim 2 , wherein an SiO 2  layer of the second DBR directly contacts the second surface of the substrate. 
     
     
         5 . The LED of  claim 4 , wherein the second DBR comprises an SiO 2  layer as the lowermost layer opposite to the SiO 2  layer directly contacting the second surface of the substrate. 
     
     
         6 . The LED of  claim 1 , further comprising a reflective metal layer covering the second DBR. 
     
     
         7 . The LED of  claim 6 , further comprising a protective layer disposed on the second surface of the substrate,
 wherein the reflective metal layer is disposed between the second DBR and the protective layer.   
     
     
         8 . The LED of  claim 1 , further comprising a transparent conductive layer disposed between the second conductivity-type semiconductor layer and the first DBR. 
     
     
         9 . The LED of  claim 8 , wherein the transparent conductive layer comprises a refractive index-grading layer having an index of refraction that decreases in a gradual or stepwise manner in a direction extending away from the second conductivity-type semiconductor layer. 
     
     
         10 . The LED of  claim 8 , wherein the transparent conductive layer comprises indium tin oxide (ITO) or ZnO. 
     
     
         11 . The LED of  claim 8 , wherein:
 the transparent conductive layer is formed on the substrate by a deposition process comprising thermal deposition, electron beam deposition, ion beam-assisted deposition, or sputtering; and   the substrate is disposed at an angle with respect to a source or a target during the deposition process, the transparent conductive layer formed on the angled substrate comprising a lower index of refraction than a transparent conductive layer formed by deposition on a substrate disposed at a normal position with respect to the source or the target.   
     
     
         12 . The LED of  claim 8 , wherein the transparent conductive layer has a lower specific resistance than the second conductivity-type semiconductor layer. 
     
     
         13 . The LED of  claim 8 , further comprising a second electrode disposed on the transparent conductive layer. 
     
     
         14 . The LED of  claim 1 , wherein the non-blue wavelength range comprises a longer wavelength than that of light generated in the active layer and being in at least a partial region of the visible spectrum. 
     
     
         15 . The LED of  claim 14 , wherein the non-blue wavelength range comprises a green to red wavelength range. 
     
     
         16 . The LED of  claim 1 , wherein the second DBR comprises a reflectivity of at least 90% with respect to light of a first wavelength in a blue wavelength range, light of a second wavelength in a green wavelength range, and light of a third wavelength in a red wavelength range. 
     
     
         17 . The LED of  claim 1 , wherein the substrate has an area of at least 90,000 μm 2 . 
     
     
         18 . The LED of  claim 17 , wherein the substrate has an area of at least 1 mm 2 . 
     
     
         19 . A light-emitting diode (LED) package, comprising:
 a mounting plane;   the LED according to  claim 1  arranged on the mounting plane; and   a phosphor covering the LED, the phosphor configured to convert a wavelength of light emitted from the LED.