THE ELECTRICAL-CONDUCTIVITY PROPERTIES OF AMORPHOUS THIN-FILM OF EVAPORATED GE-40 S-60 DURING AND AFTER LIGHT EXPOSURE

The electrical conductivity of amorphous thin films of vacuum evaporat ed Ge40S60 have been determined during and after light exposure and at different temperatures. The time dependence of the electrical conduct ivity measured in darkness or when exposed to light has been studied f or amorphous Ge40S60 thin films with different thicknesses. Photocondu ctivity started at values higher than those of saturated dark conducti vities and both gradually decreased to saturation with time. For any t hickness, increased durations of light soaking yielded temperature dep endence on dark conductivity, characterized by decreasing conductiviti es and increasing activation energies. The results were explained on t he basis that the conduction takes place in the extended states, the p ositive and negative defects centred at S, carrier mobilities increase d with temperature, heterogeneous film structure and induced electron- hole-traps.