Dergiler / Turkish Journal of Physics / 2005 / Cilt: 29 - Sayı: 2
Composition Dependence of Photoconductivity in Amorphous Thin Films of Se.80-xTe.20Gex
- Sayfa
- 91–96
- DOI
- —
Özet
The present paper reports the dependence on composition of photoconductivity in vacuum evaporated thin films of amorphous Se.80-xTe.20Gex (x = .05, .10, .15 and .20). Temperature dependence of conductivity in dark as well as in presence of light show that conduction is through a thermally activated process in both cases. The activation energy is found to decrease with increase in light intensity, indicating shift of the Fermi level with intensity. A correlation between activation energy and the pre-exponential factor is observed in all the compositions, which could be fitted to the Meyer-Neldel rule. Measurements on the dependence of photoconductivity on intensity show that photoconductivity increases with intensity as a power law, where the power is found to be between 0.5 and 1.0. The photosensitivity sph/sd increases with Ge concentration. This is explained in terms of the decrease in the density of defect states with increase of Ge content in a-Se.80-xTe.20Gex. This is consistent with the conclusions reported in the literature by dielectric loss measurements.
Abstract
The present paper reports the dependence on composition of photoconductivity in vacuum evaporated thin films of amorphous Se.80-xTe.20Gex (x = .05, .10, .15 and .20). Temperature dependence of conductivity in dark as well as in presence of light show that conduction is through a thermally activated process in both cases. The activation energy is found to decrease with increase in light intensity, indicating shift of the Fermi level with intensity. A correlation between activation energy and the pre-exponential factor is observed in all the compositions, which could be fitted to the Meyer-Neldel rule. Measurements on the dependence of photoconductivity on intensity show that photoconductivity increases with intensity as a power law, where the power is found to be between 0.5 and 1.0. The photosensitivity sph/sd increases with Ge concentration. This is explained in terms of the decrease in the density of defect states with increase of Ge content in a-Se.80-xTe.20Gex. This is consistent with the conclusions reported in the literature by dielectric loss measurements.