Abstract
This paper reports photoelectrical properties of (As30Sb15Se55)(100-x)Te-x amorphous chalcogenide films (0 <= x <= 12.5 at.%) through measurements of 'steady state' and 'transient' photocurrents. The composition dependence of the steady state photocurrent at room temperature shows that the photoconductivity increases while the photosensitivity decreases with increasing Te content. A study of photoconductivity of (As30Sb15Se55)(100-x)Te-x at different levels of light intensity reveals that, the photoconductivity increases exponentially with increase in light intensity. The Photocurrent (I-ph) when plotted against light intensity (G) follows a power law (I-ph = G(gamma)) the exponent gamma for (As30Sb15Se55)(100-x)Te-x films has been found nearly 0.5 suggesting bimolecular recombination. The transient photoconductivity shows that the lifetime of the carrier decreases with increasing the light intensity. This decrease suggests that the photoconductivity mechanism in our samples was controlled by the transition trapping processes. The increase of Te content results in a monotonic decrease in the band gap and the free carrier life time of (As30Sb15Se55)(100-x)Te-x thin films. These results were interpreted on the basis of the chemical-bond approach. (C) 2007 Elsevier B.V. All rights reserved.