Photoelectrical Properties of Thermally Deposited Amorphous As50Se50 Films
Abstract
The excitation spectrum, steady-state and transient characteristics of photoconductivity in amorphous thermally deposited chalcogenide AsSe films were studied. Besides the excitation of nonequilibrium holes by optical transitions from the valence band tail to the conduction band an additional channel of hole generation from a donor-like defect state with energy Ed — Ev = 1.5 eV was revealed. The defect is associated with the presence of homopolar As–As bonds. The steady-state and transient photoconductivity characteristics are adequately interpreted in the frame of a model, in which transport and recombination of nonequilibrium holes are controlled by exponentially distributed hole traps with the distribution parameter kT* = 0.039 eV.