Analytical solution of the inverse problem of a spectrophotometer absorbing layer on an absorbing substrate with a dielectric layer

On the example of a two-layer structure of a semiconductor–insulator–semiconductor the possibility of an analytical determination of the optical parameters and thickness of the upper layer on the reflection spectrum envelope at normal incidence of light is considered. It is very difficult to calculate these functions even in the case of absence of the transition zones between the layers. Mismatching envelopes calculated and measured reflection coefficients in certain areas of the spectra indicates the presence of inhomogeneous surface and transition zones in real structures $\mathrm{рSi}$–$\mathrm{SiO}_2$–$\mathrm{cSi}$.