Steady state and transient photoconductivity measurements in a-Se_(90-x)Sb_(10)In_x thin films

摘要

Amorphous thin films of Se_(90-x)Sb_(10)In_x (0≤x≤15) have been prepared by electron beam evaporation method. The steady state and transient photoconductivity measurements on the thin films of Se_(90-x)Sb_(10)In_x (0≤x≤15) were carried out at different levels of light intensities (500 lx-5000 lx) at room temperature (301 K). The plot of photocurrent (I_(ph)) versus light intensity (F) follows a power law I_(ph)∞F~γ. The value of exponent y lies between 0.5 and 1.0, which indicates there exists a continuous distribution of localized states in the mobility gap of Se_(90-x)Sb_(10)In_x (0≤x≤15) thin films. For transient photoconductivity, when the samples were illuminated with light, the photocurrent reaches the maximum value during the first 5 s of exposure time and thereafter, it starts decreasing and becomes stable after 15 min 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 α-Se_(75)Sb_(10)In_(15) is higher than the parent system α-Se_(90)Sb_(10). The photosensitivity shows a minimum value at 5 atomic percentage of indium (In) concentration, which is explained based on chemically ordered network model and the topological model.