Group iii nitride single crystal substrate

Abstract

A group III nitride single crystal substrate including a main surface, the main surface including: a center; a periphery; an outer region whose distance from the center is greater than 30% of a first distance, the first distance being a distance from the center to the periphery; and an inner region whose distance from the center is no more than 30% of the first distance, wherein a ratio (v A −v B )/v B is within the range of ±0.1%, wherein v A is a minimum value of peak wave numbers of micro-Raman spectra in the inner region; and v B is an average value of peak wave numbers of micro-Raman spectra in the outer region.

1 . A method for producing an aluminum nitride single crystal substrate, the method comprising, in the sequence set forth:
 (a) thermally treating a base substrate at a constant temperature of 1000 to 2300° C. for at least 60 seconds, wherein the base substrate is an aluminum nitride single crystal substrate comprising a main surface; and   (b) growing an aluminum nitride single crystal layer over the main surface by means of vapor phase epitaxy, wherein the main surface has a surface roughness of no more than 0.5 nm in terms of arithmetical mean height Sa.   
     
     
         2 . The method according to  claim 1 ,
 wherein the thermal treatment in the (a) is carried out while supplying a halogen gas, a hydrogen halide gas, and/or ammonia gas.   
     
     
         3 . The method according to  claim 1 ,
 wherein the thermal treatment in the (a) is carried out at the constant temperature of 1000 to 1700° C.   
     
     
         4 . The method according to  claim 1 ,
 wherein the vapor phase epitaxy in the (b) is hydride vapor phase epitaxy.   
     
     
         5 . The method according to  claim 1 ,
 wherein the thermally treating in (a) is carried out at a constant temperature within the range of ±100° C. from a temperature of the substrate in (b).