Photo-Electrical Properties Of Semiconducting Se-Sb-In Thin Films

Abstract

The objective of this research project was to analyze the photo-degradation of the photocurrent of the electron beam evaporated amorphous semiconducting Se90-xSb10Inx (0 ≤ x ≤ 15) thin films (α-Se90-xSb10Inx). The photo-induced effects in amorphous semiconducting Se90-xS10Inx (0 ≤ x ≤ 15) thin films were studied using two approaches: steady state and transient photoconductivity. The degradation of photocurrent has been explained on the basis of theoretical models. The steady state analysis has been performed by plotting the photocurrent (Iph) versus light intensity (F) and this variation follows a power law Iph=Fy. 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 quickly reaches the maximum value and thereafter, it starts decreasing with the exposure period and becomes stable after approximately 15 minutes of exposure. This kind of phenomenon is termed as photodegradation of photocurrent. The results have been explained on the basis of charged defect model and the inter-cluster interaction model. High photocurrents are found for α-Se75Sb10In15 system, which is even higher than the parent system Se₉₀Sb₁₀. The influence of bias voltage on the dark current and photocurrent of the Se90-xSb10Inx (0 ≤ x ≤ 15) thin films is also investigated. Both the dark and photocurrent increase with increase in the bias voltage. The compositional dependence of dark conductivity, photoconductivity and the photosensitivity shows a minimum at 5 atomic percentage of Indium (In) concentration, which has been explained based on chemically ordered network model and the topological model.