STEADY STATE PHOTOCONDUCTIVITY IN a-Se 90 Ge 10-x In x THIN FILMS

Temperature and intensity dependence of photoconductivity is studied in a-Se 90 Ge 10-x In x 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 γ 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-Se 90 Ge 10-x In x 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