The photoluminescence, photoconductivity and absorption in GaSe0.9Te0.1 alloy crystals have been investigated as a function of temperature and external electric field. It has been observed that the exciton peaks shift to lower energy in GaSe0.9Te0.1 alloy crystals compared to GaSe crystals. The long wavelength tails of interband photoluminescence, photoconductivity and absorption spectra are determined by the free exciton states and show an Urbach-Martienssen-type dependence to the photon energy. The maxima of the extrinsic photoluminescence and photoconductivity spectra were found to be determined by the acceptor centers with an energy of E-A = E-V+0.19 eV formed by the polytypism and defects complexes that include Se and Te anions. (C) 2008 Elsevier B.V. All rights reserved.