EPITAXIAL SUBSTRATE FOR SEMICONDUCTOR ELEMENT, AND METHOD OF MANUFACTURING EPITAXIAL SUBSTRATE FOR SEMICONDUCTOR ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide an epitaxial substrate for a semiconductor element which has high withstanding voltage characteristics and in which deterioration in crystal quality caused by diffusion of a p-type impurity is favorably suppressed.

SOLUTION: An epitaxial substrate 10 for a semiconductor element is configured by forming a group-III nitride layer group on a base substrate 1 made of a (111)-oriented single crystal silicon so that a (0001) crystal plane is substantially parallel to the substrate surface of the base substrate. The epitaxial substrate 10 has: a buffer layer 8 configured by laminating a plurality of unit structures each including a composition modulation layer 3 configured by laminating a first unit layer 31 and a second unit layer 32 having different compositions repeatedly and alternately, and an intermediate layer 5 formed on the composition modulation layer and made of group-III nitride containing Al; a channel layer 9a formed immediately above the buffer layer; and a barrier layer 9b formed on the channel layer. A p-type impurity is introduced intentionally to at least one of the intermediate layers included in the buffer layer to make the p-type impurity diffused from a first layer be present in adjacent layers.

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