Molecular coatings of nitride semiconductors for optoelectronics, electronics, and solar energy harvesting

Abstract

Gallium nitride based semiconductors are provided having one or more passivated surfaces. The surfaces can have a plurality of thiol compounds attached thereto for enhancement of optoelectronic properties and/or solar water splitting properties. The surfaces can also include wherein the surface has been treated with chemical solution for native oxide removal and/or wherein the surface has attached thereto a plurality of nitrides, oxides, insulating compounds, thiol compounds, or a combination thereof to create a treated surface for enhancement of optoelectronic properties and/or solar water splitting properties. Methods of making the gallium nitride based semiconductors are also provided. Methods can include cleaning a native surface of a gallium nitride semiconductor to produce a cleaned surface, etching the cleaned surface to remove oxide layers on the surface, and applying single or multiple coatings of nitrides, oxides, insulating compounds, thiol compounds, or a combination thereof attached to the surface.

What is claimed is: 
     
         1 . A surface-treated semiconductor comprising:
 a monolayer comprising a plurality of dithiol compounds attached to a metal catalyst and to a nitride-based semiconductor surface,   wherein the surface of the nitride-based semiconductor has a plurality of nanowire nanostructures that have been etched to remove oxide layers on the surface;   wherein a first thiol group of at least one of the dithiol compounds of the plurality binds a metal atom of the nitride-based semiconductor surface and the second thiol group of the at least one dithiol compounds of the plurality coordinates an atom of the metal catalyst;   wherein surface dangling bonds and nitrogen vacancies are passivated by the dithiol monolayer.   
     
     
         2 . The surface-treated semiconductor of  claim 1 , wherein the plurality of dithiol compounds includes dithiols having from 2 to 20 carbon atoms. 
     
     
         3 . The surface-treated semiconductor of  claim 1 , wherein the dithiol compounds have a backbone with one to three carbons. 
     
     
         4 . The surface-treated semiconductor of  claim 1 , wherein the metal catalyst is selected form the group consisting of Pd, Pt, Ni, Au, Ag, and Cu, or a combination thereof. 
     
     
         5 . The surface-treated semiconductor of  claim 1 , wherein the nanowires comprise a Group III metal nitride. 
     
     
         6 . The surface-treated semiconductor of  claim 5 , wherein the nitride-based semiconductor is selected from the group consisting of binary, quaternary, quinternary, and ternary (B, Al,Ga,In,Ti)N alloys. 
     
     
         7 . The surface-treated semiconductor of  claim 1 , wherein one or more of the plurality of dithiol compounds is attached to a sidewall of the nanowires. 
     
     
         8 . The surface-treated semiconductor of  claim 1 , further comprising one or more insulating compounds attached to the nitride-based semiconductor surface. 
     
     
         9 . The surface-treated semiconductor of  claim 8 , wherein the insulating compounds are selected from the group consisting of parylene and polymer-based photoresists. 
     
     
         10 . The surface-treated semiconductor of  claim 1 , further comprising one or more monothiols having a structure according to formula I, a derivative thereof, or a combination thereof: 
       
         
           
           
               
               
           
         
         wherein R 2  is a C 1 -C 20  alkyl or heteroalkyl group, optionally including one or more substituents. 
       
     
     
         11 . The surface-treated semiconductor of  claim 1 , wherein the monolayer comprises 1,2-ethanedithiol, the nitride-based semiconductor is an alloy having the chemical formula of Al a In b Ga c N x As y P z  where x is non-zero; a, b, c, x, y, and z are real numbers from 0 to 1; a+b+c is about 1, and x+y+z is about 1, and the metal catalyst is Ni, Pd, or Pt. 
     
     
         12 . A method of surface-treating a semiconductor to remove surface localized defect states originating from dangling bonds, nitrogen vacancies, and surface oxides, the method comprising:
 cleaning a native surface of a nitride-based semiconductor with acetone to produce a cleaned semiconductor surface, wherein the native surface of the nitride-based semiconductor comprises a plurality of nanowires;   etching the cleaned semiconductor surface to remove oxide layers to produce an etched semiconductor surface, and   dipping the etched semiconductor surface into a solution comprising dithiol compounds; whereby a plurality of dithiol compounds self-assemble to form a monolayer attached to the semiconductor surface; whereby the monolayer passivates dangling bonds and nitrogen vacancies on the nitride-based semiconductor; and   dipping the passivated surface in an organic solution of a metal catalyst metal atoms, whereby a first thiol group of at least one dithiol compound of the plurality is bound to a metal atom of the nitride-based semiconductor surface and the second thiol group of the at least one dithiol compound of the plurality coordinates an atom of the metal catalyst.   
     
     
         13 . The method of  claim 12 , wherein the solution includes dithiol compounds having a structure according to formula II: 
       
         
           
           
               
               
           
         
         wherein R 3  is a C 1 -C 20  alkyl or heteroalkyl group, optionally including one or more substituents, and 
         wherein R 4  is hydrogen or a C 1 -C 20  alkyl or heteroalkyl group, optionally including one or more substituents. 
       
     
     
         14 . The method of  claim 12 , wherein the dithiol compounds have a backbone with one to three carbons. 
     
     
         15 . The method of  claim 12 , wherein the metal catalyst is selected from the group consisting of Pd, Pt, Ni, Au, Ag, and Cu, or a combination thereof. 
     
     
         16 . The method of  claim 12 , wherein the nanowires comprise a Group III metal nitride. 
     
     
         17 . The method of  claim 12 , wherein the dithiol compounds comprise 1,2-ethanedithiol, the nitride-based semiconductor is an alloy having the chemical formula of Al a In b Ga c N x As y P z  where x is non-zero; a, b, c, x, y, and z are real numbers from 0 to 1; a+b+c is about 1, and x+y+z is about 1, and the metal catalyst is Ni, Pd, or Pt.