Steady state photoconductivity in a-Se80-xTe20Gex thin films

The steady state photoconductivity of vacuum evaporated thin films of amorphous Se80-xTe20Gex (x = 5, 10, 15 and 20) has been investigated. The measurements of temperature dependence of dark conductivity (sigma(d)) and photoconductivity (sigma(ph)) show that the conduction is through a thermally activated process in both the cases. The activation energy decreases with the increase in light intensity. This indicates the shift of Fermi level with intensity. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0. The photosensitivity (sigma(Ph)/sigma(d)) increases with the increase of Ge concentration which indicates that the density of defect states decreases with the increase of Ge in a-Se80-xTe20Gex. This is consistent with the conclusions reported in the literature by dielectric loss measurements.