A process by which a thin "epitaxial" layer of single-crystal material is deposited on single-crystal substrate; epitaxial growth occurs in such way that the crystallography structure of the substrate is reproduced in the growing material; also crystalline defects of the substrate are reproduced in the growing material. Although crystallography structure of the substrate is reproduced, doping levels and the conductivity type of an epitaxial layer is controlled independently of the substrate; e.g. The epitaxial layer can be made more pure chemically than the substrate.