A model of hopping and band DC photoconduction in doped crystals

Expressions for the screening length and the ambipolar diffusion length are derived, for the first time, for the case where hopping conduction and ban d conduction coexist in semiconductors with hydrogen-like impurities. A met hod is proposed for calculating the diffusion coefficient of electrons (hol es) hopping between impurity atoms from data on the Hall effect, in the cas e where the hopping and band conductivities are equal. An interpretation is given of available experimental data on hopping photoconduction between ac ceptors (Ga) and donors (As) in p-Ge at T = 4.2 K doped by a transmutation method. It is shown that the relative magnitude of the mobilities of electr ons hopping between donors and holes hopping between acceptors can be found from the hopping photoconductivity measured as a function of the intensity of band-to-band optical carrier excitation. (C) 2000 MAIK "Nauka/Interperi odica".