Reversible photoinduced change of photoconductivity in amorphous chalcogenide films

Prolonged exposure to strongly absorbed light decreases the photoconductivity of well-annealed amorphous chalcogenide (Se, ${\mathrm{As}}_2$ ${\mathrm{Se}}_3$, and ${\mathrm{As}}_2$ ${\mathrm{S}}_3$) films, similar to the behavior observed in hydrogenated amorphous silicon and organic amorphous polysilanes. This change is removed by annealing near the glass transition temperature. The reversible change in photoconductivity appears to be an intrinsic effect in amorphous semiconductors. The optically induced defect-creation reactions responsible for this, and for light-induced changes in ac conductivity, are discussed in detail.