Method for producing group iii nitride wafers and group iii nitride wafers

Abstract

The present invention discloses a method of removing contaminant from group III nitride single-crystal wafers. The method involves annealing a wafer to concentrate a contaminant in a region of the crystal near the surface of the crystal and removing some of the crystal near the surface that contains at least a portion of the region containing concentrated contaminant. The resultant thinner wafer therefore has less contaminant in it.

What is claimed is: 
     
         1 . A method of removing a contaminant from a group III nitride single-crystalline wafer comprising:
 a. annealing the wafer, which has a N-face and a group III-face, in an ambient containing ammonia vapor for a time at a temperature and pressure that concentrate a contaminant toward the group III-polar face, thereby forming a region of concentrated contaminant in the group III-polar face; and   b. removing a sufficient amount of the crystalline wafer at the group III-polar face to reduce a thickness of the crystalline wafer and to remove at least a portion of the region of concentrated contaminant;   c. wherein the contaminant is selected from an alkali metal and an alkaline earth metal.   
     
     
         2 . The method of  claim 1 , wherein the contaminant comprises at least one of sodium and lithium. 
     
     
         3 . The method of  claim 1 , wherein the contaminant comprises potassium. 
     
     
         4 . The method of  claim 1 , wherein the contaminant comprises magnesium. 
     
     
         5 . The method of  claim 1 , wherein sufficient ammonia vapor is present to suppress decomposition of the wafer. 
     
     
         6 . The method of  claim 1 , wherein the contaminant is positively charged. 
     
     
         7 . The method of  claim 1 , wherein the annealing conditions also reduce a concentration of a heavy metal at both the N face and the group III face. 
     
     
         8 . The method of  claim 7 , wherein the heavy metal is selected from the group consisting of Ti, Cr, Fe, Ni, and Co. 
     
     
         9 . The method of  claim 1 , wherein the annealing is performed at a temperature greater than or equal to 1100° C. 
     
     
         10 . The method of  claim 1 , wherein the annealing is performed at a temperature greater than or equal to 1200° C. 
     
     
         11 . The method of  claim 1 , wherein the annealing is performed at a sufficiently high temperature to reduce a number of point defects in the wafer. 
     
     
         12 . The method of  claim 1 , wherein the group III nitride single-crystalline wafer comprises gallium. 
     
     
         13 . The method of  claim 1 , wherein the group III nitride single-crystalline wafer was formed using an ammonothermal process. 
     
     
         14 . A single-crystalline wafer formed by an ammonothermal process having, at an N-face of the wafer, a concentration of lithium about equal to or less than 4×10 13  or a concentration of potassium about equal to or less than 3×10 14  cm −3 . 
     
     
         15 . A single-crystalline wafer formed by an ammonothermal processing having, at an N-face of the wafer, a concentration of chromium about equal to or less than 6×10 14  cm −3  or a concentration of nickel of about equal to or less than 1×10 16  cm −3 .