Method for fabricating a III nitride film, an underlayer for fabricating a III nitride film and a method for fabricating the same underlayer

Abstract

A method for fabricating a Group III nitride film is provided, including the steps of preparing a substrate, forming an underfilm and then forming the Group III nitride film on the underfilm. The underfilm is a Group III nitride including at least 50 atomic percent of elemental Al for each of the Group III elements of the underfilm Group III nitride. The surface of the underfilm includes a contoured portion and a flat region, and less than 50% of the surface is occupied by the flat region.

We claim:  
     
         1 . An underfilm for fabricating a Group III nitride film, including a contoured surface structure including flat regions, wherein 50% or less of said contoured surface structure is occupied by said flat regions, said underfilm comprising a first Group III nitride including at least 50 atomic percent of elemental Al with respect to all of the Group III elements constituting the first Group III nitride.  
     
     
         2 . An underfilm as defined in  claim 1 , wherein the first Group III nitride constituting the underfilm includes at least 70 atomic percent elemental Al with respect to all of the Group III elements constituting the first Group III nitride.  
     
     
         3 . An underfilm as defined in  claim 2 , wherein the first Group III nitride constituting the underfilm is AlN.  
     
     
         4 . An underfilm as defined in  claim 1 , wherein no more than 10% of the contoured surface structure of the underfilm is occupied by said flat regions.  
     
     
         5 . An underfilm as defined in  claim 1 , wherein the contoured surface structure except the flat regions includes {101} facets.