Coalesced nanowire structures with interstitial voids and method for manufacturing the same

Abstract

A semiconductor device, such as an LED, includes a plurality of first conductivity type semiconductor nanowire cores located over a support, a continuous second conductivity type semiconductor layer extending over and around the cores, a plurality of interstitial voids located in the second conductivity type semiconductor layer and extending between the cores, and first electrode layer that contacts the second conductivity type semiconductor layer.

1 . (canceled) 
     
     
         2 . A semiconductor device, comprising:
 a plurality of first conductivity type semiconductor nanowire cores located over a support;   an active region shell surrounding each nanowire core;   a first continuous layer of a second conductivity type semiconductor extending over and surrounding the cores;   a second continuous layer of the second conductivity type semiconductor extending over and surrounding the cores; and   a first electrode layer that contacts the second continuous layer of the second conductivity type semiconductor;   wherein:   the device comprises a light emitting diode (LED) device;   the active region shell comprises at least one quantum well and the first continuous layer of second conductivity type semiconductor contacts the at least one quantum well to form a light emitting junction at each nanowire core surrounded by the at least one quantum well shell;   the second continuous layer of the second conductivity type semiconductor extends over and surrounds the first continuous layer of second conductivity type semiconductor;   a portion of a space between adjacent active region shells is completely filled with the second continuous second conductivity type semiconductor layer; and   the second continuous second conductivity type semiconductor layer has height variations such that a top surface of the second continuous second conductivity type semiconductor layer has high points over the underlying nanowire cores and low points between the underlying nanowire cores.   
     
     
         3 . The device of  claim 2 , wherein the height variations in the top surface of the second continuous second conductivity type semiconductor layer create light-scattering variations in index of refraction. 
     
     
         4 . The device of  claim 2 , wherein the top surface of the second continuous second conductivity type semiconductor layer is not planar due to curvature of the underlying nanowire cores and interstitial nanowire core space topography. 
     
     
         5 . The device of  claim 4 , wherein the height variations between the high points and the low points is 5 to 50% of a total height. 
     
     
         6 . The device of  claim 2 , further comprising a plurality of interstitial voids located within the second continuous layer of the second conductivity type semiconductor and extending between the nanowire cores, wherein the interstitial voids are completely enclosed on top and sides by the second continuous layer of the second conductivity type. 
     
     
         7 . The device of  claim 6 , wherein the first electrode layer that contacts the second continuous layer of the second conductivity semiconductor does not extend into the interstitial voids. 
     
     
         8 . The device of  claim 6 , wherein the device is comprises a photonic crystal having a photonic crystal lattice constant of ½ of spacing of the nanowire cores. 
     
     
         9 . The device of  claim 2 , wherein:
 the first conductivity type comprises n-type;   the second conductivity type comprises p-type;   the first electrode layer comprises a p-electrode layer;   the support comprises an n-type semiconductor buffer layer on a substrate;   the substrate comprises an n-Si or sapphire substrate;   the buffer layer comprises an n-GaN or n-AlGaN layer;   the nanowire cores comprise n-GaN nanowires epitaxially extending from portions of the buffer layer surface exposed through openings in an insulating mask layer on the buffer layer;   the at least one quantum well comprises an InGaN quantum well; and   the second continuous layer of second conductivity type semiconductor comprises a p-GaN layer.   
     
     
         10 . The device of  claim 9 , further comprising a second electrode layer which electrically connects to the n-type nanowire cores. 
     
     
         11 . The device of  claim 9 , wherein the first continuous layer of second conductivity type semiconductor comprises a p-AlGaN layer.