Electrical and photoelectrical properties of Ag–In–Se thin films evaporated by e-beam technique

Abstract

In this study, the electrical and photoelectrical properties of the Ag–In–Se thin films deposited by the e-beam technique have been investigated by carrying out temperature dependent conductivity, photoconductivity under different illumination intensities and photoresponse measurements between 380 and 1050 nm, as a function of annealing temperature. The measured conductivity values of the films at room temperature depending on the annealing temperatures vary in the range 1.9 × 10−6–5.2 Ω−1 cm−1. Annealing the films above 200 °C results in degenerate thin films. Photoconductivity of the films increases with illumination intensity and its value reaches about 300 times dark conductivity values as the illumination intensity is increased from 17 to 113 mW cm−2 for as-grown samples. The relation between photocurrent and excitation intensity is of Iph ∝ ϕn-type. n values varying in the range of 0.96 and 1.55 imply the supralinear photoconductivity with the two-centre model. The spectral distribution of photoconductivity shows three maxima located at 1.57, 1.77 and 2.01 eV, which was governed by the splitting of p-like levels in the valence band including the effects of a tetragonal crystalline field (ΔCF) and spin–orbit (ΔSO) interaction. The band gap energies of as-grown and the 200 °C annealed films are determined to be 1.57 eV and 1.68 eV, respectively.