Stationary hopping photoconduction among multiply charged impurity atoms in crystals

A derivation of the equation for the hopping current of electrons and holes (electron vacancies) among impurities of a single species in three charge states [(−1), (0), and (+1)] is given in the continuum approximation. The screening length of an electrostatic field and the diffusion length of charge carriers are calculated. The dependence of the effective lifetime of electrons hopping among impurities relative to (−1)→(+1) transitions [and of holes relative to (+1)→(−1) transitions] on the degree of compensation and the rate of interimpurity photoexcitation, which stimulates the formation of ions, is obtained. The calculations of the dependence of the hopping photoconductivity on photoexcitation rate are consistent with known experimental data, which have not previously found a theoretical explanation. Fiz. Tverd. Tela (St. Petersburg) 40, 1805–1809 (October 1998)