Crystal growth method, crystal growth apparatus, group-III nitride crystal and group-III nitride semiconductor device

Abstract

A crystal growth method, comprising the steps of: a) bringing a nitrogen material into a reaction vessel in which a mixed molten liquid comprising an alkaline metal and a group-III metal; and b) growing a crystal of a group-III nitride using the mixed molten liquid and the nitrogen material brought in by the step a) in the reaction vessel, wherein a provision is made such as to prevent a vapor of the alkaline metal from dispersing out of the reaction vessel.

1 - 6 . (canceled).  
   
   
       7 . A crystal growth apparatus, comprising: 
 a reaction vessel holding a mixed molten liquid comprising an alkaline metal and a group-III metal;    a first heating device heating the mixed molten liquid so as to enable crystal growth therein; and    a second heating device heating above the surface of the mixed molten liquid so as to prevent the vapor of the alkaline metal above the surface of the mixed molten liquid from condensing.    
   
   
       8 . A crystal growth apparatus comprising: 
 a reaction vessel holding a mixed molten liquid comprising an alkaline metal and a group-III metal; and    a heating device heating a zone through which a nitrogen material is supplied externally into said reaction vessel.    
   
   
       9 . The apparatus as claimed in  claim 7 , wherein: 
 another reaction vessel is provided outside of said reaction vessel;    the nitrogen material is brought into the inner reaction vessel through the thus-provided outer reaction vessel; and    a provision is made such as to allow the nitrogen material to be brought into said inner reaction vessel from said outer reaction vessel, and, also, to cause the vapor of the alkaline metal to stay inside said inner reaction vessel.    
   
   
       10 . The apparatus as claimed in  claim 8 , wherein the nitrogen material is supplied horizontally or from a direction below the horizontal direction.  
   
   
       11 - 18 . (canceled).  
   
   
       19 . A crystal growth apparatus comprising: 
 a reaction vessel in which crystal growth is performed of a group-i nitride comprising a group-III metal and a nitrogen from an alkaline metal, a substance comprising the group-III metal, and a substance comprising the nitrogen; and    a unit maintaining a growth condition for a crystal of the group-III nitride at a condition at which the crystal growth starts; then,    maintaining the growth condition at a condition at which the crystal growth stops; and, then,    again setting the condition at which the crystal growth starts.    
   
   
       20 . The apparatus as claimed in  claim 19 , wherein said unit comprises a heating device heating a zone in which a crystal of the group-III nitride grows.  
   
   
       21 . The apparatus as claimed in  claim 19 , wherein said unit comprises a pressure control device controlling an effective pressure of the substance comprising the nitrogen in a form of a gas in a zone in which a crystal of the group-III nitride grows.  
   
   
       22 - 27  (canceled).  
   
   
       28 . A crystal growth apparatus, comprising: 
 a liquid holding vessel in which a mixed molten liquid comprising an alkaline metal and a substance comprising a group-III metal is formed; and    a unit growing in said liquid holding vessel a crystal of a group-III nitride comprising the group-III metal and nitride from the mixed molten liquid and a substance comprising the nitride,    wherein said liquid holding vessel has an inner shape such as to create a local concentration distribution of dissolved nitrogen in the mixed molten liquid.    
   
   
       29 . The apparatus as claimed in  claim 28 , wherein said inner shape of said liquid holding vessel is such that the cross sectional area becomes smaller downward.  
   
   
       30 . The apparatus as claimed in  claim 28 , wherein said inner shape of said liquid holding vessel is such that the cross sectional area is reduced partially.  
   
   
       31 . The apparatus as claimed in  claim 28 , wherein said inner shape of said liquid holding vessel is such that the cross sectional area becomes smaller downward first, and, then, the cross sectional area is uniform downward from the mid level.  
   
   
       32 . The apparatus as claimed in  claim 28 , wherein said inner shape of said liquid holding vessel is such that the cross sectional area becomes smaller downward first, and, then, the cross sectional area becomes larger downward from the mid level.  
   
   
       33 . The apparatus as claimed in  claim 28 , wherein said unit comprises a heating device heating the temperature inside said liquid holding vessel so as to enable the crystal growth therein.  
   
   
       34 . The apparatus as claimed in  claim 31 , wherein said unit comprises a plurality of heating devices for creating a predetermined temperature difference between an upper part and a lower part of said liquid holding vessel.  
   
   
       35 - 58  (canceled).