Optoelectronic, photoelectric and dc conductivity of amorphous As2S3
thin films prepared by thermal evaporation are investigated. Absorption
coefficient as well as photoconductivity spectral dependence is used to estimate
the band gap. The temperature dependence of dc conductivity and steady state
photoconductivity revealed a discontinuity at 150 K. A comparative study of the
film properties before and after irradiation demonstrated the light-induced
changes. Photodarkening, with metastable and transient components, is
observed. The photoconductivity kinetics indicated that the new localized states,
created by illumination, dominate the recombination process in a similar
manner to the original states. The similarity in behaviours obtained before and
after irradiation suggests that photochemical changes are produced by
illumination.