Steady state photoconductivity in a-Se90Ge10-xInx thin films

Temperature and intensity dependence of photoconductivity is studied in a-Se90Ge10-xInx thin films prepared by vacuum evaporation. Temperature dependence of photoconductivity shows a maximum at a particular temperature. The study carried out on intensity dependence of photoconductivity shows that the values of gamma is found to be between 0.5 and 1.0 for all the samples. This indicates that there exists a continuous distribution of localized state in the mobility gap of a-Se90Ge10-xInx thin films. Composition dependence of steady state photoconductivity shows that photoconductivity as well as photosensitivity is found to be minimum at 4 at. % of In. A discontinuity in various electrical parameters at 4 at. % of In is related to formation of mechanically stabilized structure at a particular average coordination number 2.2. This is consistent with the theory of Phillips and Thorpe for the topological model in case of chalcogenide glasses.