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 evaporated Ge40S60 have been determined during and after light exposure and at different temperatures. The time dependence of the electrical conductivity measured in darkness or when exposed to light has been studied for amorphous Ge40S60 thin films with different thicknesses. Photoconductivity started at values higher than those of saturated dark conductivities and both gradually decreased to saturation with time. For any thickness, increased durations of light soaking yielded temperature dependence on dark conductivity, characterized by decreasing conductivities and increasing activation energies. The results were explained on the basis that the conduction takes place in the extended states, the positive and negative defects centred at S, carrier mobilities increased with temperature, heterogeneous film structure and induced electron-hole-traps.