Saturation of the metastable defect density in amorphous silicon semiconductor

초록

We report on a study of the metastable defect creation under pulsed light illumination in undoped hydrogenated amorphous silicon. Defect generation rate, saturation value of defect density, N<inf>sat</inf>, and characteristic time, τ<inf>c</inf>, required to reach N<inf>sat</inf> have been investigated. Results show approximately a t1/2 time-dependence of the defect generation, different from a t1/2 time-dependence under continuous wave light illumination. It is observed that the saturation value of the defect density is about one order of magnitude higher than by cw illumination in device-quality films. It is found that the characteristic time decreases with hydrogen content and micro structure fraction, but increases with substrate temperature. Results are discussed within the framework of existing models for the light-induced defect generation.