METHOD FOR PRODUCING A GROUP III NITRIDE SEMICONDUCTOR SINGLE CRYSTAL AND METHOD FOR PRODUCING A GaN SUBSTRATE

Abstract

A method for producing a Group III nitride semiconductor single crystal, includes forming a mask layer on an underlayer, to thereby form a seed crystal in which a portion of the underlayer is covered with the mask layer and in which the remaining portion of the underlayer is not covered with the mask layer, etching the remaining portion, and growing a Group III nitride semiconductor single crystal on the seed crystal.

What is claimed is: 
     
         1 . A method for producing a Group III nitride semiconductor single crystal, the method comprising:
 forming a mask layer comprising Al X In Y Ga (1-X-Y) N (0<X, 0≦Y, X+Y≦1) on an underlayer, to thereby form a seed crystal in which a portion of the underlayer is covered with the mask layer and in which the remaining portion of the underlayer is not covered with the mask layer;   etching the remaining portion of the underlayer in a melt containing at least an alkali metal, a facet plane of the underlayer is exposed through melting back; and   growing a Group III nitride semiconductor single crystal on the seed crystal in a molten mixture containing at least a Group III metal and an alkali metal, the Group III nitride semiconductor single crystal is grown on the seed crystal such that the facet plane is buried with the Group III nitride semiconductor single crystal.   
     
     
         2 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , further comprising:
 forming trenches by removing an area of the mask layer through a full thickness and a corresponding area of the underlayer through a partial thickness.   
     
     
         3 . The method for producing the Group III nitride semiconductor single crystal according to  claim 2 , wherein,
 in the remaining portion etching, bottom planes of the trenches and inclined planes of the trenches are exposed,   in the Group III nitride semiconductor single crystal growth, the Group III nitride semiconductor single crystal is grown from the bottom planes of the trenches, the inclined planes of the trenches, and the surface of the mask layer.   
     
     
         4 . The method for producing the Group III nitride semiconductor single crystal according to  claim 3 , wherein,
 in the Group III nitride semiconductor single crystal growth, dislocations are merged and combined together.   
     
     
         5 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , wherein, in the remaining portion etching, the c-plane of the underlayer is exposed through melting back. 
     
     
         6 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , wherein the facet plane is a {1,0,−1,1} plane. 
     
     
         7 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , wherein, in the mask layer formation, the mask layer is formed of an AlGaN layer. 
     
     
         8 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , wherein, in the mask layer formation, the Al compositional proportion X in the mask layer is adjusted to 0.02 to 1.00. 
     
     
         9 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , wherein, in the mask layer formation, the thickness of the mask layer is adjusted to 2 nm to 2 μm. 
     
     
         10 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , further comprises:
 forming a GaN layer as an underlayer, before formation of the mask layer.   
     
     
         11 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , the underlayer is a GaN substrate. 
     
     
         12 . The method for producing the Group III nitride semiconductor single crystal according to  claim 1 , the underlayer is a GaN layer formed on a sapphire substrate. 
     
     
         13 . The method for producing the Group III nitride semiconductor single crystal according to  claim 2 , wherein, a plurality of the trenches are arranged in the mask layer in a lattice-like pattern. 
     
     
         14 . The method for producing the Group III nitride semiconductor single crystal according to  claim 2 , wherein, in the trenches formation, a plurality of trenches having an opening width of 1 μm to 1,000 μm are formed. 
     
     
         15 . A method for producing a Group III nitride semiconductor single crystal, the method comprising:
 preparing a seed crystal having an Al-containing Group III nitride semiconductor layer as an outermost layer;   growing a Group III nitride semiconductor single crystal on the seed crystal through reaction of a molten mixture containing at least a Group III metal and an alkali metal with a gas containing at least nitrogen, while melting back of the seed crystal is suppressed to 500 nm or less.   
     
     
         16 . The method for producing the Group III nitride semiconductor single crystal according to  claim 15 , wherein the Al-containing Group III nitride semiconductor layer is an AlGaN layer. 
     
     
         17 . The method for producing the Group III nitride semiconductor single crystal according to  claim 16 , wherein the Group III metal is Ga, the alkali metal is Na, and the Group III nitride semiconductor crystal to be grown is a GaN crystal. 
     
     
         18 . The method for producing the Group III nitride semiconductor single crystal according to  claim 17 , wherein the seed crystal is a stacked structure having a GaN layer, and an AlGaN layer stacked on the GaN layer. 
     
     
         19 . A method for producing a GaN substrate, the method comprising:
 forming a mask layer comprising Al X In Y Ga (1-X-Y) N (0<X, 0≦Y, X+Y≦1) on an underlayer, to thereby form a seed crystal in which a portion of the underlayer is covered with the mask layer and in which the remaining portion of the underlayer is not covered with the mask layer;   etching the remaining portion of the underlayer in a melt containing at least an alkali metal, a facet plane of the underlayer is exposed through melting back;   growing a GaN single crystal on the seed crystal in a molten mixture containing at least a Group III metal and an alkali metal, the GaN single crystal is grown on the seed crystal such that the facet plane is buried with the GaN single crystal; and   removing the GaN single crystal from the seed crystal.