Ultra-small vertical cavity surface emitting laser (vcsel) and arrays incorporating the same

Abstract

A laser diode includes a semiconductor structure having an n-type layer, an active region, and a p-type layer. One of the n-type and p-type layers includes a lasing aperture thereon having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers. First and second contacts are electrically connected to the n-type and p-type layers, respectively. The first and/or second contacts are smaller than the lasing aperture in at least one dimension. Related arrays and methods of fabrication are also discussed.

That which is claimed: 
     
         1 . A laser diode, comprising:
 a semiconductor structure comprising an n-type layer, an active region, and a p-type layer, one of the n-type and p-type layers comprising a lasing aperture having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers; and   first and second contacts electrically connected to the n-type and p-type layers, respectively, wherein each of the first and second contacts is smaller than the lasing aperture in at least one dimension in plan view.   
     
     
         2 . The laser diode of  claim 1 , wherein a respective contact area of each of the first and second contacts in plan view is smaller than an aperture area of the lasing aperture. 
     
     
         3 . The laser diode of  claim 1 , wherein the laser diode is free of wire bond pads that are electrically connected to the first and second contacts. 
     
     
         4 . The laser diode of  claim 1 , further comprising:
 a lateral conduction layer comprising a surface including the semiconductor structure thereon, wherein the lateral conduction layer is distinct from the n-type and p-type layers, and wherein one of the first and second contacts is on the surface of the lateral conduction layer adjacent the semiconductor structure and outside of the n-type and p-type layers.   
     
     
         5 . The laser diode of  claim 4 , wherein the laser diode is freed of a native substrate thereof. 
     
     
         6 . The laser diode of  claim 5 , further comprising:
 a non-native substrate including the laser diode on a surface thereof,   wherein the non-native substrate comprises electrically insulating and/or thermally conducting characteristics, and wherein the laser diode is free of electrical connections through the non-native substrate.   
     
     
         7 . The laser diode of  claim 6 , wherein the n-type and p-type layers comprise first and second Bragg reflector layers, respectively, and wherein the laser diode comprises a vertical cavity surface emitting laser (VCSEL). 
     
     
         8 . A Light Detection and Ranging (LIDAR) emitter, comprising:
 a plurality of laser diodes arranged in an array on a surface of a non-native substrate, wherein each of the laser diodes comprises:
 a semiconductor structure comprising an n-type layer, an active region, and a p-type layer, one of the n-type and p-type layers comprising a lasing aperture having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers; and 
 first and second contacts electrically connected to the n-type and p-type layers, respectively, wherein the first and second contacts are smaller than the lasing aperture in at least one dimension in plan view. 
   
     
     
         9 . The LIDAR emitter of  claim 8 , wherein the first and second contacts of each of the laser diodes comprise anode and cathode contacts, respectively, and further comprising:
 electrically conductive thin-film interconnects that electrically connect the anode and cathode contacts of respective subsets of the plurality of laser diodes anode-to-cathode.   
     
     
         10 . The LIDAR emitter of  claim 9 , further comprising:
 a plurality of driver transistors, wherein the respective subsets of the plurality of laser diodes are electrically connected in series with respective driver transistors of the plurality of driver transistors, and wherein the respective driver transistors are configured to control operation of the respective subsets of the plurality of laser diodes independent of one another.   
     
     
         11 . The LIDAR emitter of  claim 10 , wherein the respective subsets of the plurality of laser diodes define rows or columns of the array, and wherein the respective driver transistors are configured to operate the rows or columns at different output power levels. 
     
     
         12 . The LIDAR emitter of  claim 11 , wherein a concentration of the plurality of laser diodes at a first portion of the array is less than a concentration of the plurality of laser diodes at a second portion of the array. 
     
     
         13 . The LIDAR emitter of  claim 8 , wherein the plurality of laser diodes are free of a native substrate thereof. 
     
     
         14 . A method of fabricating a laser diode, the method comprising:
 separating a semiconductor structure comprising an n-type layer, an active region, and a p-type layer from a native substrate thereof; and   providing first and second contacts electrically connected to the n-type and p-type layers, respectively,   wherein one of the n-type and p-type layers comprises a lasing aperture having an optical axis oriented perpendicular to a surface of the active region between the n-type and p-type layers, and wherein each of the first and second contacts is smaller than the lasing aperture in at least one dimension in plan view.   
     
     
         15 . The method of  claim 14 , wherein a respective contact area of each of the first and second contacts in plan view is smaller than an aperture area of the lasing aperture. 
     
     
         16 . The method of  claim 14 , wherein the laser diode is free of wire bond pads that are electrically connected to the first and second contacts. 
     
     
         17 . The method of  claim 14 , further comprising:
 forming the semiconductor structure on a surface of a lateral conduction layer, wherein the lateral conduction layer is distinct from the n-type and p-type layers, and wherein one of the first and second contacts is on the surface of the lateral conduction layer adjacent the semiconductor structure and outside of the n-type and p-type layers.   
     
     
         18 . The method of  claim 17 , further comprising:
 providing the laser diode on a surface of a non-native substrate, wherein the non-native substrate comprises electrically insulating and/or thermally conducting characteristics, and wherein the laser diode is free of electrical connections through the non-native substrate.   
     
     
         19 . The method of  claim 18 , wherein the first and second contacts comprise anode and cathode contacts, respectively, and further comprising:
 forming electrically conductive thin-film interconnects on the non-native substrate that electrically connect the anode and cathode contacts of the laser diode to cathode and anode contacts, respectively, of adjacent laser diodes on the surface of the non-native substrate.   
     
     
         20 . The method of  claim 18 , wherein the n-type and p-type layers comprise first and second Bragg reflector layers, respectively, and wherein the laser diode comprises a vertical cavity surface emitting laser (VCSEL).