Anisotropy of thermal excitation from impurities and nonequilibrium currents in homogeneous pyroelectric semiconductors

The anisotropy of the thermal excitation probability of electrons from the impurities in a pyroelectric crystal causes the appearance of the electric current if the nonequilibrium is being kept. Namely, the inequality of chemical potentials of free and bound electrons is considered to be the reason of this nonequilibrium. The value of the current is calculated for the one-phonon excitation of the electrons from shallow hydrogen-like impurities the depth of which is less than the Debye frequency or the same order of it.