Effect of light intensity and temperature on the recombination mechanism in a-(Ge₂₀Se₈₀)_99.5Cu_0.5thin film

Abstract

The temperature dependence of electrical conductivity measurements has been studied in the dark as well as in the presence of light in vacuum evaporated thin films of (Ge20Se80)99.5Cu0.5. The dark conductivity increases exponentially with temperature. The temperature dependence of steady state photoconductivity at different intensities indicates that photoconductivity is also thermally activated. These measurements ensure the presence of mono- and bimolecular recombination regions. Transient photoconductivity measurements at different temperatures and light intensities show that the photocurrent passes through a maximum before attaining the steady state. The results have been explained in terms of the multiple-trapping model with photoconductivity kinetics determined by trap-controlled recombination.