Saturation of Optical Degradation in a-Si:H Films with Different Morphologies

The saturation effect of the optical degradation in hydrogenated amorphous silicon films (a-Si:H) deposited at various temperatures T s has been studied by means of photoconductivity measurements. It was confirmed that the saturation is mainly related to the simultaneous annealing at a higher light-soaking temperature T 1 (≧20°C) as well as the depletion of the weak Si-Si bonds at lower T 1 (≦0°C). The weak bond density (10 16 ∼10 18 /cm 3 ) estimated from the low-temperature saturation effect decreases with increasing T s corresponding to the growth of Si clusters.