Effect of Ag additive on the photoconductive properties of Se-Ge glassy alloys

The temperature and intensity dependence of photoconductivity measurements has been studied in amorphous thin films of Se80−xGe20Agx (x=0, 5, 10) prepared by vacuum evaporation. The dark conductivity (σd) increases and the activation energy (ΔE) decreases as the Ag concentration increases in the present glass composition. The photoconductivity (σph) also increases with an increase in Ag concentration. However, the photosensitivity (σph/σd) decreases with an increase in Ag concentration. This indicates that the lifetime of the excess carriers is less in the sample containing a higher concentration of Ag. Lesser lifetimes further indicate a higher recombination rate for the excess carriers, which is expected when the density of defect states (DOS) is more. One can therefore expect that the DOS increases with the increase in Ag concentration in amorphous thin films of Se80−xGe20Agx (x=0, 5, 10). This is in agreement with the variation of the pre-exponential factor (σ0) with Ag concentration.