Poole–Frenkel effect in chalcogenide semiconductors with various crystalline structures

The results of investigation of electrical conductivity of a large group of chalcogenide semiconductors having the layered, cubic, and orthorhombic structures in strong electric fields up to 10$^5$ V/cm are presented. The revealed increase in electrical conductivity $\sigma$ in strong electric fields has been explained by the Frenkel thermionic ionization. This has made it possible, along with other parameters (for example, activation energy and trap concentration, charge-carrier mean free path, permittivity), to evaluate the concentration and mobility of charge carriers in semiconductors under study. It has been shown that in strong electric fields in semiconductors, when the thermionic ionization of the traps occurs, their permittivity $\varepsilon$, which is caused by the electron polarization, is determined by the simple formula $\varepsilon=n^2$, where $n$ is the refractive index of light.