Package-integrated thin film led

Abstract

LED epitaxial layers (n-type, p-type, and active layers) are grown on a substrate. For each die, the n and p layers are electrically bonded to a package substrate that extends beyond the boundaries of the LED die such that the LED layers are between the package substrate and the growth substrate. The package substrate provides electrical contacts and conductors leading to solderable package connections. The growth substrate is then removed. Because the delicate LED layers were bonded to the package substrate while attached to the growth substrate, no intermediate support substrate for the LED layers is needed. The relatively thick LED epitaxial layer that was adjacent the removed growth substrate is then thinned and its top surface processed to incorporate light extraction features. There is very little absorption of light by the thinned epitaxial layer, there is high thermal conductivity to the package because the LED layers are directly bonded to the package substrate without any support substrate therebetween, and there is little electrical resistance between the package and the LED layers so efficiency (light output vs. power input) is high. The light extraction features of the LED layer further improves efficiency.

1 . A method comprising:
 providing a wafer comprising light emitting diode (LED) layers grown on a growth substrate, the LED layers comprising a first epitaxial layer of a first conductivity type, a second epitaxial layer of a second conductivity type, and an active layer disposed between the first and second epitaxial layers;   dicing the wafer;   after dicing the wafer, removing the growth substrate; and   after removing the growth substrate, roughening the LED layers.   
     
     
         2 . The method of  claim 1  wherein roughening the LED layers comprises roughening a top surface of the LED layers. 
     
     
         3 . The method of  claim 1  wherein roughening the LED layers comprises photo-electrochemically etching the LED layers. 
     
     
         4 . The method of  claim 1  wherein dicing the wafer comprises dicing the wafer into separate LED elements. 
     
     
         5 . The method of  claim 1  wherein the LED layers are less than 50 microns thick. 
     
     
         6 . The method of  claim 1  further comprising after dicing the wafer, mounting a plurality of LED dice on a package substrate, wherein neighboring LED dice are spaced apart from each other. 
     
     
         7 . The method of  claim 1  wherein the LED layers are III-P layers. 
     
     
         8 . A device comprising:
 a semiconductor structure comprising a III-nitride active layer disposed between an n-type layer and a p-type layer;   a first metal contact in direct contact with the p-type layer, wherein the first metal contact is reflective;   a transparent conductor in direct contact with the n-type layer; and   a second metal contact in direct contact with the transparent conductor, wherein the second metal contact comprises a plurality of metal contact regions spaced apart from each other.   
     
     
         9 . The device of  claim 8  wherein the transparent conductor is an oxide. 
     
     
         10 . The device of  claim 8  further comprising a wire bonded to the second metal contact. 
     
     
         11 . The device of  claim 8  wherein a surface of portions of the semiconductor disposed between the plurality of metal contact regions is roughened. 
     
     
         12 . A method comprising:
 growing LED layers on a growth substrate, the LED layers comprising an active layer disposed between an n-type layer and a p-type layer;   removing the growth substrate;   forming a transparent conductive layer on a surface of the LED layers exposed by removing the growth substrate; and   forming a metal contact over the transparent conductive layer, wherein the metal contact comprises a plurality of metal contact regions separated by regions where the metal contact is removed or not formed.   
     
     
         13 . The method of  claim 12  wherein forming a metal contact comprises:
 forming a mask; 
 depositing metal over the mask; and 
 dissolving the mask such that metal disposed over the mask is removed. 
 
     
     
         14 . The method of  claim 12  wherein forming a metal contact comprises:
 depositing metal on the transparent conductive layer; and 
 lithographically patterning the metal. 
 
     
     
         15 . The method of  claim 12  further comprising bonding a wire to the metal contact. 
     
     
         16 . The method of  claim 12  further comprising roughening a surface of the LED layers in the regions where the metal contact is removed or not formed.