Photoconductivity in a-Se90Ge10-xInx thin films

Temperature dependence of conductivity is studied in dark Lis well as in presence of light in amorphous thin films of Se90Ge10-xInx (x = 0, 2, 4, 6, 8 and 10) prepared by vacuum evaporation technique. The dark conductivity increases exponentially with temperature, between 293 and 373 K, indicating that the conductivity is a thermally activated process. Temperature dependence of conductivity in presence of light at different intensities indicate that photoconductivity is also thermally activated in the above temperature range in all the samples studied. The activation energy of photoconduction is found to decrease with the increase in the intensity which indicates the shift of the Fermi level on light shining due to splitting of Fermi level into quasi-Fermi levels. Transient photoconductivity measurements at different temperatures and intensities indicate that the decay of photoconductivity is quite slow. A persistent photocurrent is also observed which increases at higher temperatures. This is attributed to light-induced effects in these materials. Photoconductivity decay, even after subtraction of persistent photoconductivity, is found to be non-exponential in the present case indicating the presence of continuous distribution of defect states. (C) 2003 Published by Elsevier Science Ltd.