Effect of Annealing on Photoinduced Absorption in Amorphous Silicon Films Prepared at High Deposition Rates

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Abstract
The effects of annealing on the photoinduced optical absorption (PA) of hydrogenated amorphous silicon films prepared at a high deposition rate of ∼4.5 nm/s have been investigated in relation to the changes in structural and optical properties induced by annealing. The variation of the thermoresistivity with the hydrogen effusion from the film is compared with that in low-deposition-rate films, and it is concluded that trapped hole states near the valence band (A-centers) inducing most of the PA are correlated with the presence of hydrogen in a-Si:H films. The structural relaxation produced by annealing up to 400°C is accompanied by a reduction in the gap and tail state density near the conduction-band edge.