Photoconductivity and photoinduced absorption in a-Si:F and a-Si:H

The photoconductivity (PC) and photoinduced absorption (PA) of RF glow discharge a-Si:F and a-Si:H samples is reported. The value of the room temperature PC of a-Si:F is lower by some four orders of magnitude relative to that of a-Si:H, but the PA of a-Si:F is found to be significantly higher than that of a-Si:H. This indicates that the recombination rate of excess carriers is lower in a-Si:F than it is in a-Si:H, yet a larger fraction of the excess carriers are trapped in the band tails of a-Si:F, leading to its low PC. From the analysis of our PA data, we also determine the position of the mobility edge with respect to the extrapolated band edge in a-Si:H.