Specific temperature-related features of photoconductivity relaxation in PbSnTe:In films under interband excitation

The time dependences of variations in the photoconductivity of PbSnTe:In films in the range of $T\approx$ 19–25 K upon interband excitation are studied. It is found that the character of conductivity relaxation after switch-off of illumination depends on the duration and intensity of the preceding illumination. In this case, the characteristic times of relaxation for various modes of illumination can differ by more than an order of magnitude. The obtained results are discussed in the context of a model assuming the presence of a quasicontinuous spectrum of capture levels in the band gap of PbSnTe:In and also a possible effect on the parameters of these levels of the ferroelectric phase transition, the temperature of which is found to be in the temperature range under study.