Dark and photoconductivity of amorphous Se–Te–Pb thin films

Amorphous thin films of Se80−xTe20Pbx (0<x<2) have been prepared by a thermal evaporation technique. Dark and photoconductivity of the samples was measured at different temperatures. The value of the DC activation energy ΔEa and the optical band gap Egopt for Se80Te20 was found to be ∼0.67 and ∼1.68 eV, respectively. The addition of a small amount of Pb (0.6 at.%) to the Se–Te system decreases ΔEa (∼0.3 eV) and Egopt (∼1.39 eV) considerably. However, further addition of Pb (up to 2 at.%) does not cause much change in these parameters. The photoconductivity is found to increase with increasing temperature and light intensity. The square-root dependence of photocurrent on the illumination intensity indicates that the recombination process is bimolecular. The photosensitivity and the differential lifetime are also reported for Se80−xTe20Pbx (0<x<2) thin films.