Nanowire LED Structure and Method for Manufacturing the Same

Abstract

A method for ablating a first area of a light emitting diode (LED) device which includes an array of nanowires on a support with a laser is provided. The laser ablation exposes a conductive layer of the support that is electrically connected to a first conductivity type semiconductor nanowire core in the nanowires, to form a first electrode for the LED device. In embodiments, the nanowires are aligned at least 20 degrees from the plane of the support. A light emitting diode (LED) structure includes a first electrode for contacting a first conductivity type nanowire core, and a second electrode for contacting a second conductivity type shell enclosing the nanowire core, where the first electrode and/or at least a portion of the second electrode are flat.

What is claimed is: 
     
         1 . A method comprising ablating a first area of an light emitting diode (LED) device with a laser, the LED device comprising an array of nanowires on a support, wherein the laser ablation exposes a conductive layer of the support that is electrically connected to a first conductivity type semiconductor nanowire core in the nanowires, to form a first electrode for the LED device. 
     
     
         2 . The method of  claim 1 , wherein the nanowires are aligned at least 20 degrees from the plane of the support. 
     
     
         3 . The method of  claim 1 , wherein the laser ablation is performed to provide a flatness of the first electrode of at least <200 nm peak to valley in a 1 μm×1 μm area. 
     
     
         4 . The method of  claim 1 , further comprising forming a second electrode for the LED structure wherein the second electrode is electrically connected to a second conductivity type semiconductor nanowire shell in the nanowires. 
     
     
         5 . The method of  claim 1 , wherein the first conductivity type semiconductor nanowire core is enclosed by the second conductivity type semiconductor shell for forming a pn or pin junction that in operation provides an active region for light generation. 
     
     
         6 . The method of  claim 5 , wherein the first conductivity type comprises n-type, the second conductivity type comprises p-type. 
     
     
         7 . The method of  claim 6 , wherein the first electrode comprises an n-electrode layer. 
     
     
         8 . The method of  claim 7 , wherein the n-electrode layer comprises a buffer layer from which the nanowire core is grown during production of the array of nanowires. 
     
     
         9 . The method of  claim 8 , wherein the buffer layer comprises at least one of gallium nitride or aluminum gallium nitride. 
     
     
         10 . The method of  claim 8 , wherein the support further comprises a dielectric masking layer, such that cores protrude from the buffer layer through openings in the masking layer, and the shells are located on the masking layer. 
     
     
         11 . The method of  claim 9 , wherein the support further comprises a substrate layer beneath the buffer layer. 
     
     
         12 . The method of  claim 11 , wherein the substrate layer comprises Al 2 O 3 . 
     
     
         13 . The method of  claim 8 , wherein the support layer further comprises a reflective layer. 
     
     
         14 . The method of  claim 13 , wherein the reflective layer comprises Ag. 
     
     
         15 . The method of  claim 6 , wherein the second electrode is a p-electrode layer that is electrically connected to the p-type nanowire shells. 
     
     
         16 . The method of  claim 15 , wherein the second electrode comprises a transparent conductive oxide (TCO) layer. 
     
     
         17 . The method of  claim 16 , wherein the TCO layer is deposited by chemical vapor deposition. 
     
     
         18 . The method of  claim 16 , wherein the transparent conductive oxide layer comprises an Indium Tin Oxide (ITO) layer that is deposited by evaporation. 
     
     
         19 . The method of  claim 1 , wherein the support is transparent. 
     
     
         20 . The method of  claim 1  wherein the laser ablation is performed using a pulsed laser. 
     
     
         21 . The method of  claim 20  wherein the spot size of the laser pulse is between 20 and 150 microns. 
     
     
         22 . The method of  claim 21  wherein the spot size is between 10 and 50 microns. 
     
     
         23 . The method of  claim 22  wherein the spot size is between 20 and 40 microns. 
     
     
         24 . The method of  claim 20  wherein the laser is a modular fiber laser. 
     
     
         25 . The method of  claim 20  wherein the energy of each pulse is between 0.01 and 1 J/cm 2 . 
     
     
         26 . The method of  claim 25  wherein the energy per light pulse is between 0.1 and 0.5 J/cm2. 
     
     
         27 . The method of  claim 26  wherein the energy per light pulse is between 0.15 and 0.4 J/cm2 
     
     
         28 . A light emitting diode (LED) structure comprising
 (i) a plurality of devices on a support layer that comprises a substrate, a buffer layer, and a dielectric mask layer, wherein the devices comprise a first conductivity type semiconductor nanowire core that is in electrical contact with the buffer layer and an enclosing second conductivity type semiconductor shell, wherein the core and the shell are configured to form a pn or pin junction that in operation provides an active region for light generation and the shell is insulated from the buffer layer by the mask layer, and   (ii) a first electrode for contacting the first conductivity type core and   (iii) a second electrode for contacting the second conductivity type shell, wherein the first electrode and/or at least a portion of the second electrode are flat.