Degradation and annealing characteristics of amorphous silicon-hydrogen alloys after a long-time test

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Abstract
The effect of long time (up to 1000 h) repeated light exposure combined with annealing at different temperatures (25–200 °C) on the photoconductivity of an intrinsic amorphous silicon-hydrogen alloy has been investigated. It was found that the degradation process was not entirely reversible and that the photoconductivity decay was enhanced after each test cycle. A new annealing behavior was observed; that is, the photoconductivity of the degraded films did not show any sign of recovery when annealed below the degradation temperature (25 °C) for 800 h, but started to improve slowly when annealed at a temperature above 50 °C. The light-soaking effect was also studied by using different light intensities and substrate temperatures. It was found that the nonreciprocity relation always holds, and the degradation is much improved when tested at a higher temperature. The bond-breaking model with a distribution of dangling-bond distance is used to explain all these results.