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 (σd) and photoconductivity (σph) 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 (σph/σd) 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.
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