Low Etch Pit Density (EPD) Semi-Insulating GaAs Wafers

Abstract

A method for manufacturing wafers using a low EPD crystal growth process and a wafer annealing process is provided that results in GaAs/InGaP wafers that provide higher device yields from the wafer.

1 . A method for manufacture a gallium based material with a low etch pit density (EPD), the method comprising:
 forming polycrystalline gallium based compounds; and   performing vertical gradient freeze crystal growth using the polycrystalline gallium based compounds wherein the gallium based crystal has an etch pit density of less than 900 per square centimeter.   
   
   
       2 . The method of  claim 1 , wherein the crystal has an etch pit density of about 600 per square centimeter. 
   
   
       3 . The method of  claim 2  further comprising forming a gallium arsenide substrate from the gallium based crystal. 
   
   
       4 . The method of  claim 2  further comprising forming a indium phosphide, gallium phosphide or other III-IV substrates from the gallium based crystal. 
   
   
       5 . The method of  claim 1 , wherein performing vertical gradient freeze crystal growth further comprises controlling a shape of the melt/crystal interface during the vertical gradient freeze crystal growth wherein the shape is concave or convex to a melt front. 
   
   
       6 . The method of  claim 1 , wherein performing vertical gradient freeze crystal growth further comprises controlling a crystallization velocity during the vertical gradient freeze crystal growth wherein the crystallization velocity is between 2 and 16 mm/hour. 
   
   
       7 . The method of  claim 1 , wherein performing vertical gradient freeze crystal growth further comprises controlling a temperature gradient at a melt/crystal interface during the vertical gradient freeze crystal growth wherein the temperature gradient at the melt/crystal interface is between 0.1 to 2 degrees Celsius. 
   
   
       8 . The method of  claim 1 , wherein performing vertical gradient freeze crystal growth further comprises controlling a total temperature gradient during the vertical gradient freeze crystal growth wherein the total temperature gradient is between 1 and 5 degrees Celsius. 
   
   
       9 . A method for manufacture a substrate with low light defects, the method comprising:
 forming a gallium arsenide based substrate;   annealing the gallium arsenide based substrate using a single step annealing;   controlling the oxygen into a surface of the gallium based substrate during the annealing process; and   removing a portion of the surface of the gallium based substrate to form a gallium arsenide based substrate having a predetermined oxygen content level and a light point defect of less than  1  per square centimeter per gallium arsenide based substrate with a particle size of greater than 0.3 micrometers.   
   
   
       10 . The method of  claim 9 , wherein annealing the gallium arsenide based substrate further comprises controlling a heating rate during the annealing wherein the heating rate is 900 to 1050 degrees Celsius over 10 to 48 hours. 
   
   
       11 . The method of  claim 9 , wherein annealing the gallium arsenide based substrate further comprises controlling a platform temperature during the annealing wherein the platform temperature is 900 to 1050 degrees Celsius. 
   
   
       12 . The method of  claim 9 , wherein annealing the gallium arsenide based substrate further comprises controlling a cooling rate during the annealing wherein the cooling rate is to room temperature in 6 to 24 hours. 
   
   
       13 . A gallium based substrate, comprising:
 a substrate having an etch pit density of less than 900 per square centimeter using a vertical gradient freeze process; and   the substrate having less than 120 light point defects and a light point defect particle size of less than 0.3 micrometers.   
   
   
       14 . The substrate of  claim 13 , wherein the substrate is gallium arsenide (GaAs). 
   
   
       15 . The substrate of  claim 13 , wherein the substrate is indium phosphide, gallium phosphide or other III-V compounds. 
   
   
       16 - 30 . (canceled)