Steady state and transient photoconductivity measurements in a-Se90 − xSb10Inx thin films

Abstract

Amorphous thin films of Se90−xSb10Inx (0≤x≤15) have been prepared by electron beam evaporation method. The steady state and transient photoconductivity measurements on the thin films of Se90−xSb10Inx (0≤x≤15) were carried out at different levels of light intensities (500lx–5000lx) at room temperature (301K). The plot of photocurrent (Iph) versus light intensity (F) follows a power law Iph∝Fγ. The value of exponent γ lies between 0.5 and 1.0, which indicates there exists a continuous distribution of localized states in the mobility gap of Se90−xSb10Inx (0≤x≤15) thin films. For transient photoconductivity, when the samples were illuminated with light, the photocurrent reaches the maximum value during the first 5s of exposure time and thereafter, it starts decreasing and becomes stable after 15min of exposure. This kind of phenomenon is termed as photo-degradation of photocurrent. The results have been explained on the basis of charged defect model and the intercluster interaction model. The magnitude of photocurrent of the system a-Se75Sb10In15 is higher than the parent system a-Se90Sb10. The photosensitivity shows a minimum value at 5atomic percentage of indium (In) concentration, which is explained based on chemically ordered network model and the topological model.