Abstract
The long-term photocurrent decays following steady-state photo-excitation have been measured in amorphous As2Se3 (a-As2Se3) and hydrogenated amorphous silicon (a-Si:H) films as a function of temperature. The photocurrent I p(t) for a-As2Se3 is described empirically by the extended exponential law (exp(—Ct α)) and is explained by dispersive diffusion-controlled monomolecular recombination of excess neutral defects (D0); 2D0 → D+ + D−. I p(t) for a-Si:H is nearly proportional to the power law (t-β) and is explained either by a Fermi-level analysis introducing a time-dependent recombination rate, or localized-localized recombination which is dominated by a dispersive diffusion-controlled bimolecular process. It is emphasized that the dispersive diffusion of trapped carriers plays an important role in long-term non-exponential photocurrent decay in amorphous semiconductors.