Thermal quenching of thermally stimulated conductivity

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Thermal quenching of thermally stimulated conductivity has been considered theoretically assuming a model with three types of states in the bandgap of a semiconductor. It has been shown that the contribution of minority charge carriers to thermally stimulated conductivity might distort the shape of a peak or even change the number of peaks observed. Our model involves traps for majority and minority charge carriers as well as recombination centres. A set of equations is solved in a quasi-stationary approximation. For weak re-trapping of electrons and holes, an analytical solution has been obtained. Other cases have been analysed numerically. Since the minority charge carrier density may be of the same order of magnitude as the majority charge carrier density, which is observed experimentally as the inversion of polarity in the Hall effect or thermo-electromotive force, the bipolar conductivity should also be revealed in the thermally stimulated conductivity phenomenon, and this paper confirms it. The experimental thermally stimulated conductivity curves observed in single crystals of GaAs have been interpreted using the proposed model. The estimation of trap parameters taking into account the contribution of minority charge carriers has been discussed.