On the photoconductivity relaxation in ZnIn2S4

The relaxation process of photoconductivity in ZnIn2S4 is investigated together with optical quenching and thermally stimulated current. Photocurrent decays are processed by four-gate technique of photoinduced current transient spectroscopy (PICTS). A non-exponential behaviour of the decays, due to a non-linear multichannel recombination mechanism, leads to 'anomalous' PICTS spectra that in the temperature range 200 to 300 K allow to evidence a thermal emission from a centre with a repulsive potential barrier. The photoconductivity relaxation in the 80 to 200 K range is attributed to two competitive recombination channels. Models for the relaxation through both radiative and non-radiative recombination channels are proposed on the basis of optical quenching effect. In any case the recombination mechanism is dominated by energy levels exponentially distributed below the conduction band with a 'slope' of 33 eV-1. (author)