Optical and photoelectrical investigations of Ge₂₀Se₆₉Bi₁₁ thin films

Thin films of amorphous Ge₂₀Se₆₉Bi₁₁ were investigated using optical reflectance and transmittance as well as photoconductivity. The determined spectral dependencies of real part of refractive index and absorption coefficient of radiation are presented. The optical energy gap and the Urbach energy have been obtained from the absorption data. The high-frequency dependence of photoconductivity on chopping frequency of illumination intensity allowed to determine the majority carrier lifetime. Using its value as well as the measured optical parameters and the experimental sublinear dependence of photoconductivity on illumination intensity the carrier mobility was evaluated.