Gallium nitride semiconductor

Abstract

A gallium nitride based semiconductor Schottky diode fabricated from a n+ doped GaN layer having a thickness between one and six microns disposed on a sapphire substrate; an n− doped GaN layer having a thickness greater than one micron disposed on said n+ GaN layer patterned into a plurality of elongated fingers and a metal layer disposed on the n− doped GaN layer and forming a Schottky junction therewith. The layer thicknesses and the length and width of the elongated fingers are optimized to achieve a device with breakdown voltage of greater than 500 volts, current capacity in excess of one ampere, and a forward voltage of less than three volts.

1 - 20 . (canceled) 
     
     
         21 . A power semiconductor device comprising:
 a substrate;   a first gallium nitride layer of a first conductivity type disposed on the substrate, the first gallium nitride layer having a first thickness and a first doping concentration;   a second gallium nitride layer of the first conductivity type disposed on the first gallium nitride layer, the second gallium nitride layer having a second thickness and a second doping concentration lower than the first doping concentration, the second gallium nitride layer being formed in a pattern comprising a plurality of parallel, elongated finger regions extending from a common central region in opposite lateral directions; and   a first metal layer disposed on the second gallium nitride layer such that a first Schottky diode junction is formed between the first metal layer and the second gallium nitride layer, the first Schottky diode junction having a forward voltage of two volts or less.   
     
     
         22 . The power semiconductor device of  claim 21  wherein the first thickness is between one and six microns. 
     
     
         23 . The power semiconductor device of  claim 21  wherein the first conductivity type is n-type. 
     
     
         24 . The power semiconductor device of  claim 21  wherein the substrate comprises sapphire. 
     
     
         25 . The power semiconductor device of  claim 21  wherein the second thickness is greater than three microns. 
     
     
         26 . The power semiconductor device of  claim 21  wherein the first and second thicknesses are such that the diode has a reverse breakdown voltage of greater than 500 volts and a current capacity in excess of five amperes is greater than three microns. 
     
     
         27 . The power semiconductor device of  claim 21  wherein the first Schottky diode junction has a current capacity of at least four amperes. 
     
     
         28 . The power semiconductor device of  claim 21  further comprising a first ohmic metal layer disposed on at least a portion of the first gallium nitride layer, the first ohmic metal layer forming a first ohmic contact with the first gallium nitride layer. 
     
     
         29 . The power semiconductor device of  claim 28  wherein the substrate has a top surface, the first gallium nitride layer not being disposed on an area of the top surface. 
     
     
         30 . The power semiconductor device of  claim 29  further comprising a second ohmic metal layer disposed on at least a portion of the area of the substrate, first gallium nitride layer, the first ohmic metal layer forming a first ohmic contact with the first gallium nitride layer. 
     
     
         31 . The power semiconductor device of  claim 21  wherein the plurality of parallel, elongated finger regions are arranged symmetrically about the common central region. 
     
     
         32 . The power semiconductor device of  claim 21  wherein a spacing between each of the plurality of parallel, elongated finger regions has a width that results in the first Schottky diode junction having a breakdown voltage of 500 volts or greater.