Photoconductivity studies of Te-substituted Sn-Sb-Se semiconducting films

Amorphous thin films of chalcogenide Sn10Sb20Se70−X Te X (0≤X≤8) composition were deposited using the thermal evaporation technique. The dark conductivity measurement showed a thermally activated conduction process with single activation energy in a studied temperature regime. Photoconductivity showed no maxima in the measured temperature regime revealing that the material belongs to the type II photoconductor. The observed small difference between activation energy for photoconduction ΔE ph and dark conduction ΔE accounts for low photosensitivity of the material. The intensity variation of the photocurrent obeys the power law with the exponent γ∼0.56–0.64 revealing the dominant bimolecular recombination mechanism in the studied compositions. Transient photoconductivity revealed that initial rise of the photocurrent becomes slow with tellurium content in the sample. The change in the shape of the transient photocurrent with composition is qualitatively explained based upon change in defect statistics introduced by the tellurium content in the sample. The decay process after the initial decay was found to be nonexponential and is described with a differential life time of charge carrier that showed a decreasing trend with the tellurium content in the sample.