Photoelectrical properties of semiconducting amorphous Se-Te-Sb thin films

摘要

The electrical properties of Se70Te30-xSbx (x = 0, 2, 4, 6, 8) amorphous thin films preparedby thermal evaporation technique have been studied. The dark conductivity (σd), chargecarrier concentration (nσ) and photoconductivity (σph) increases as the concentration of Sbadditive increases upto x = 6 at. % in a-Se70Te30-xSbx thin films. The activation energy(ΔΕ) and photosensitivity (σph/σd) decreases sharply after Sb incorporation. As the Sbconcentration is further increased (when x=8 at. %) a reverse in the trend has beenobserved for all these parameters. Intensity dependence of photoconductivity has also beenstudied at 303 K and follows a power law as σph ∝ Fγ, where γ lies between 0.5 and 1. Thedifferential life time (τd) is determined from the decay of photocurrent with time. Thedifferential life time increases as the Sb concentration increases upto x = 6 at. %. Theresults are explained on the basis of increase in the density of localized states present inthe mobility gap and in terms of the electron affinity values of the various constituents ofSe-Te-Sb thin films.