Current-voltage characteristic of a narrow-band semiconductor taking into account ionization of impurities

The current-voltage characteristic of a material with a narrow conduction band in a strong electric field is studied taking into account ionization of deeply lying impurities in the model, in which collisions of charge carriers are described in the Fokker-Planck approximation. The results are compared with analogous results obtained in the v approximation. It is shown that the results obtained earlier in the v approximation coincide with our results to within similar to 5%. It is noted that the Fokker-Planck model additionally provides the temperature dependence of the current-voltage characteristic.