Effect of phase separation on the kinetics of photocurrent relaxation in Sn-Sb-Se glassy films.

The effects of phase separation on the structure and photoconductivity kinetics in Sn(x)Sb(20)Se(80-x) (x = 10,11,12.5) glassy films have been studied. Crystalline peaks for SnSe(2), Sn(2)Sb(4)Se(8) and Sn(4)Sb(4)Se(10) phases are found in x = 12.5 films, while Sb(2)Se(3) is the other major phase revealed from x-ray diffraction studies. The optical gap remains constant at 1.55 eV for x = 10,11 samples and then decreases to 1.50 eV for the x = 12.5 film, while a blueshift in reflectivity maxima (R(max)) has been observed with Sn content. An increase in room temperature conductivity and a decrease in dc activation energy with Sn content have been observed. Bimolecular recombination is the dominant recombination process under steady state illumination for all of the samples. Decay of photocurrent (after cessation of light) fits well to a stretched exponential function; the decay time constant and dispersion parameter have been discussed. The growth of network connectivity with an increase in compositional/configurational disorder induces states in the mobility gap and affects the structure of band tails. These results have been interpreted in the light of the barrier cluster model developed for chalcogenide glasses.