Surface and bulk defects in hydrogenated amorphous silicon and silicon-based alloy films

The surface and bulk defects in a-Si:H, a-Si1-xCx:H, and a-Si1-xNx:H films were investigated by electron spin resonance (ESR) and constant photocurrent method. The thickness of the surface defective layer in a-Si:H films was determined for the first time by ESR. Applying various surface treatments, the free-surface layer proved to be much more defective than the interface layer. Both surface and bulk defect densities in a-Si1-xCx:H and a-Si1-xNx@B: H alloy films were also determined by ESR. The origin of the surface states is discussed, and the experimental results are explained by a simplified model of the distribution of surface defects.