Composite high reflectivity layer

Abstract

A high efficiency light emitting diode with a composite high reflectivity layer integral to said LED to improve emission efficiency. One embodiment of a light emitting diode (LED) chip comprises an LED and a composite high reflectivity layer integral to the LED to reflect light emitted from the active region. The composite layer comprises a first layer, and alternating plurality of second and third layers on the first layer, and a reflective layer on the topmost of said plurality of second and third layers. The second and third layers have a different index of refraction, and the first layer is at least three times thicker than the thickest of the second and third layers. For composite layers internal to the LED chip, conductive vias can be included through the composite layer to allow an electrical signal to pass through the composite layer to the LED.

We claim: 
     
         1 . A light emitting diode (LED) chip, comprising:
 an active region between an n-type layer and a p-type layer;   a composite high reflectivity layer on said n-type layer and on said p-type layer.   
     
     
         2 . The LED chip of  claim 1 , further comprising:
 a first contact in electrical contact with said n-type layer on a first side of said LED chip;   a second contact in electrical contact with said p-type layer also on said first side of said LED chip.   
     
     
         3 . The LED chip of  claim 1 , wherein said LED chip is a lateral geometry LED chip. 
     
     
         4 . The LED chip of  claim 1 , said composite high reflectivity layer comprising a first portion on said n-type layer and a second portion on said p-type layer, said first and second portions electrically isolated from one another. 
     
     
         5 . The LED chip of  claim 1 , further comprising conductive vias through said composite high reflectivity layer. 
     
     
         6 . The LED chip of  claim 1 , further comprising a first metal layer on said composite high reflectivity layer over said n-type layer and a second metal layer on said composite high reflectivity layer over said p-type layer. 
     
     
         7 . The LED chip of  claim 1 , said composite high reflectivity layer comprising:
 a first layer;   one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, said second and third layers alternating, and each of said third layers having different thicknesses compared to the other of said third layers, said third layers comprising at least a pair of layers comprising a same material and different thicknesses; and   a reflective layer on the topmost of said second and third layers.   
     
     
         8 . The LED chip of  claim 1 , further comprising a substrate on said n-type layer opposite said composite high reflectivity layer. 
     
     
         9 . The LED chip of  claim 1 , said composite high reflectivity layer comprising a plurality of layers and a conductive path through said composite layer through which an electrical signal can pass to said LED, said plurality of layers comprising at least a pair of layers comprising a same material and different thicknesses. 
     
     
         10 . The LED chip of  claim 1 , wherein said composite high reflectivity layer provides higher reflectivity to the wavelength of light emitted from said LED compared to a distributed Bragg reflector. 
     
     
         11 . The LED chip of  claim 1 , wherein said composite high reflectivity layer provides an angle averaged reflectivity greater than a quarter wavelength distributed Bragg reflector having the same number of layers. 
     
     
         12 . The LED chip of  claim 1 , further comprising a conductive grid electrically contacting said p-type layer or said n-type layer through said composite high reflectivity layer.