Origin of photoinduced metastable defects in amorphous chalcogenides

Abstract

Prolonged exposure to band-gap light decreases the photoconductivity of annealed films of amorphous chalcogenides (${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$, ${\mathrm{As}}_{3}$${\mathrm{S}}_{7}$, AsS, ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$, ${\mathrm{GeS}}_{2}$, ${\mathrm{GeSe}}_{2}$, and GeSe). This can be attributed to photoinduced metastable defects, which could act as additional trapping and/or recombination centers. These metastable centers are removed by annealing near the glass transition temperature. The kinetics of the temporal change of photocurrent during illumination are discussed in a model of defect-conserved bond switching.