Role of charged defects in the photoconductivity of Se95As5 chalcogenide glassy semiconductor with the EuF3 impurity

Abstract

The energy spectrum of local states associated with charged defects D− and D+ playing a significant role in carrier generation and recombination in the chalcogenide glassy semiconductor system Se95As5 containing EuF3 impurities is proposed based on the study of the temperature dependence of the dark conductivity and steady-state photoconductivity, current-luminance characteristic, and the spectral distribution of the photocurrent. It is shown that EuF3 impurities nonmonotonically change the concentrations of these states. Low concentrations form chemical compounds with selenium and arsenic due to the chemical activity of the rare-earth element and fluorine ions, which result in a decrease in the concentration of initial intrinsic defects. High concentrations, according to the charged-defect model, lead to a decrease in the concentration of D+ centers and an increase in the concentration of D− centers due to the presence of Eu3+ ions. Some parameters of the charged-defect model are estimated, in particular the effective correlation energy Ueff (0.6 eV) and the polaron relaxation energy (W+ = 0.4 eV, W− = 0.45 eV).