Influence of electric field on the activation energy of local levels in semiconductors with layered (GaSe) and cubic (Ga$_{2}$Se$_{3}$) structures

The results of measuring the electrical conductivity of layered crystals (GaSe, GaTe, and their solid solutions) and cubic crystals (Ga$_2$Se$_3$) in strong electric fields (up to 5 $\times$ 10$^5$ V/cm) in the temperature range of 77–300 K are presented. These results are compared with predictions of the phenomenological theory of concentration instability in semiconductors. This theory considers the role of the Frenkel effect, which is related to the thermionic ionization of traps causing instability in semiconductors with an $S$-shaped current–voltage (I – V) characteristic. Based on the results of measuring the electrical conductivity of layered and cubic crystals exhibiting the Frenkel effect and described by the theory of current instability in semiconductors, the free-carrier concentration in the aforementioned types of chalcogenide semiconductors is estimated to be $n$ = (3 $\times$ 10$^{13}$–4 $\times$ 10$^{15}$) cm$^{-3}$.