Photoinduced metastable surface effects in boron-doped hydrogenated amorphous silicon films

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Abstract
We observed metastable light-induced conductance changes in p-type hydrogenated amorphous silicon films which are different from those discovered by Staebler and Wronski. In contrast to the large metastable decrease in the dark conductance after prolonged exposure to band-gap light (Staebler–Wronski effect) we observed an increase in the dark conductance by more than a factor of 30 at room temperature. This light-induced increase can be reversed by annealing. The anomalous conductance increase is associated with the presence of a surface oxide layer because it disappears after etching the sample. We find that the enhanced conductance is due to an increase of a hole accumulation layer in the sample caused by a light-induced metastable change in the surface oxide.