COMPOSITE BASE INCLUDING SINTERED BASE AND BASE SURFACE FLATTENING LAYER, AND COMPOSITE SUBSTRATE INCLUDING THAT COMPOSITE BASE AND SEMICONDUCTOR CRYSTALLINE LAYER

摘要

A composite base of the present invention includes a sintered base and a base surface flattening layer disposed on the sintered base, and the base surface flattening layer has a surface RMS roughness of not more than 1.0 nm. A composite substrate of the present invention includes the composite base and a semiconductor crystal layer disposed on a side of the composite base where the base surface flattening layer is located, and a difference between a thermal expansion coefficient of the sintered base and a thermal expansion coefficient of the semiconductor crystal layer is not more than 4.5×10⁻⁶K⁻¹. Thereby, a composite substrate in which a semiconductor crystal layer is attached to a sintered base, and a composite base suitably used for that composite substrate are provided.