The epitaxial structures are considered with a buried layer which represent a semiconductor substrate wafer with an epitaxial film grown on its surface and with a region lying near the metallurgical substrate film boundary which differs in comparison with the substrate and the epitaxial film in level and type of doping. The transparency region of such structures corresponds to the usual IR region of the optical spectrum. The aim of this work is the development of a comparatively simple and quite general method of reproducing the profile of the carrier concentration distribution function from the reflection spectrum. 18 refs.