Patent ID: 8648351
Filing Date: 2014-02-11
Classification: C30B,H01L

Abstract:
1. An epitaxial substrate in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of said base substrate, said epitaxial substrate comprising: a buffer layer including a plurality of composition modulation layers each formed of a first composition layer made of AlN and a second composition layer made of a group-III nitride having a composition of Al a crystal layer formed on said buffer layer, wherein each of said composition modulation layers is formed so as to satisfy the relationship of: where n represents the number of laminations of each of said first composition layer and said second composition layer (n is a natural number equal to or greater than two), and x(i) represents the value of x in i-th one of said second composition layers as counted from said base substrate side, each of said second composition layers is formed so as to be in a coherent state relative to said first composition layer, said buffer layer is formed of a first lamination unit and a second lamination unit being alternately laminated, said first lamination unit is said composition modulation layer, and said second lamination unit is an intermediate layer made of AlN and formed with a thickness of 10 nm or more and 150 nm or less.