Long-time repeated photo-degradation test of amorphous silicon hydrogen alloy

The effect of the long-time (up to 1000 hrs) repeated light exposure combined with annealing at different temperature (25 ∼ 2000C) on the photoconductivity of an intrinsic amorphous silicon hydrogen alloy has been investigated. It was found that the degradation process was not entirely reversible if the annealing temperature was below the deposition temperature. The power indexes of the photoconductivity decay for some samples were larger than 1/3 which indicates that the metastable defects are generated not from direct electron-hole pair recombination but from recombination through gap states. A new annealing behavior was observed, that is the photoconductivity of the degraded films didn't show any sign of recovery when annealed below the degradation temperature (250C) for 800 hrs, but started to improve slowly when annealed at a temperature above 500C. The bond-breaking model with a distribution of dangling bond distance is used to explain all these results