Self-aligned ito dbr based p-contact for small pitch micro-led

Abstract

A micro-light emitting diode includes a substrate including at least a first portion of an n-type semiconductor layer, and a mesa structure on the substrate and characterized by a linear lateral dimension equal to or less than about 3 μm. The mesa structure includes a plurality of epitaxial layers, and a conductive distributed Bragg reflector (DBR) on the plurality of epitaxial layers. The conductive DBR includes a plurality of transparent conductive oxide layers and covers between about 80% and about 100% of a full lateral area of the plurality of epitaxial layers. The micro-LED also includes a dielectric layer on sidewalls of the mesa structure, a reflective metal layer on sidewalls of the dielectric layer and electrically coupled to the first portion of the n-type semiconductor layer, and a first metal electrode in direct contact with the conductive DBR.

What is claimed is: 
     
         1 . A micro-light emitting diode (micro-LED) device comprising:
 a substrate including at least a first portion of an n-type semiconductor layer; and   an array of micro-LEDs on the substrate and characterized by a pitch equal to or less than 4 μm, each micro-LED of the array of micro-LEDs including:
 a mesa structure including:
 a plurality of epitaxial layers; and 
 a conductive distributed Bragg reflector (DBR) on the plurality of epitaxial layers, the conductive DBR including a plurality of transparent conductive oxide layers and covering at least 80% of a full lateral area of the plurality of epitaxial layers; 
 
 a dielectric layer on sidewalls of the mesa structure; 
 a reflective metal layer on sidewalls of the dielectric layer and electrically coupled to the first portion of the n-type semiconductor layer; and 
 a first metal electrode in direct contact with the conductive DBR. 
   
     
     
         2 . The micro-LED device of  claim 1 , wherein the conductive DBR aligns with the plurality of epitaxial layers and covers the full lateral area of the plurality of epitaxial layers in the mesa structure. 
     
     
         3 . The micro-LED device of  claim 1 , wherein the plurality of transparent conductive oxide layers includes:
 a first set of indium tin oxide (ITO) layers characterized by a first refractive index; and   a second set of ITO layers characterized by a second refractive index and interleaved with the first set of ITO layers.   
     
     
         4 . The micro-LED device of  claim 3 , wherein:
 the first set of ITO layers includes crystalline ITO; and   the second set of ITO layers includes porous ITO.   
     
     
         5 . The micro-LED device of  claim 3 , wherein:
 the first set of ITO layers includes ITO nanorods in a first orientation; and   the second set of ITO layers includes ITO nanorods in a second orientation that is different from the first orientation.   
     
     
         6 . The micro-LED device of  claim 3 , wherein:
 the first refractive index is greater than 2.0 for a target wavelength; and   the second refractive index is less than 1.7 for the target wavelength.   
     
     
         7 . The micro-LED device of  claim 1 , wherein a reflectance of the conductive DBR for a target wavelength is greater than 90%. 
     
     
         8 . The micro-LED device of  claim 1 , wherein the plurality of epitaxial layers includes:
 a second portion of the n-type semiconductor layer;   an active region including one or more quantum wells configured to emit visible light; and   a p-type semiconductor layer coupled to the conductive DBR.   
     
     
         9 . The micro-LED device of  claim 1 , wherein each micro-LED of the array of micro-LEDs further includes a micro-lens on the substrate. 
     
     
         10 . The micro-LED device of  claim 1 , further comprising at least one of:
 a second metal electrode electrically coupled to the reflective metal layer and the first portion of the n-type semiconductor layer; or   a transparent conductive oxide layer electrically coupled to the first portion of the n-type semiconductor layer or the reflective metal layer.   
     
     
         11 . A micro-light emitting diode (micro-LED) comprising:
 a substrate including at least a first portion of an n-type semiconductor layer;   a mesa structure on the substrate and characterized by a linear lateral dimension equal to or less than 3 μm, the mesa structure including:
 a plurality of epitaxial layers; and 
 a conductive distributed Bragg reflector (DBR) on the plurality of epitaxial layers, the conductive DBR including a plurality of transparent conductive oxide layers and covering at least 80% of a full lateral area of the plurality of epitaxial layers; 
   a dielectric layer on sidewalls of the mesa structure;   a reflective metal layer on sidewalls of the dielectric layer and electrically coupled to the first portion of the n-type semiconductor layer; and   a first metal electrode in direct contact with the conductive DBR.   
     
     
         12 . The micro-LED of  claim 11 , wherein the conductive DBR aligns with the plurality of epitaxial layers and covers the full lateral area of the plurality of epitaxial layers in the mesa structure. 
     
     
         13 . The micro-LED of  claim 11 , wherein the plurality of transparent conductive oxide layers includes:
 a first set of indium tin oxide (ITO) layers characterized by a first refractive index; and   a second set of ITO layers characterized by a second refractive index and interleaved with the first set of ITO layers,   wherein the first set of ITO layers and the second set of ITO layers have different porosities or different nanorod orientations.   
     
     
         14 . The micro-LED of  claim 11 , wherein a reflectance of the conductive DBR for a target wavelength is greater than 90%.