Picosecond trapping of photocarriers in amorphous silicon

Abstract

Trapping of photoexcited carriers in the picosecond and subnanosecond time domains was studied by measuring the decay of photoinduced absorption (PA) in a-Si, a-Si:F, a-Si:H, and a-Si:H:F. We found that when the midgap density of states decreases, both the trapping time and its temperature dependence increase. The observed PA decays are compared to the picosecond photoconductivity decays, and the differences in the response curves are explained. The possibility that geminate recombination might explain our results is ruled out.