Saturation of the light-induced defect density in hydrogenated amorphous silicon

Abstract
We report new experimental results on the saturation of the light‐induced defect density in hydrogenated (and fluorinated) amorphous silicon. The films were illuminated near room temperature up to 5000 h with bandpass filtered red light at a carrier generation rate G of 5×1020 cm3 s1, or up to 20 h with Kr+ laser light (λ=647.1 nm) at G=3×1022 cm3 s1. The bulk defect densities Ns saturate in both cases in the vicinity of 1017 cm3. The saturation values are almost independent either of G or of temperature in the range from room temperature to about 70 °C. The illumination time to reach saturation is approximately proportional to 1/G2. These results are discussed within the framework of existing models for the light‐induced defects.