Spatial distribution of light-induced defects in hydrogenated amorphous silicon

Abstract

We have deduced the spatial distribution of defects in light-soaked hydrogenated amorphous silicon (a-Si:H) from the thickness dependence of the areal defect density using a large number of film thicknesses, ranging from 0.05 to 8.7 μm. The light soaking was done with strong white light generated by a Xe lamp with an infrared-cut filter and the defects were measured using electron spin resonance. The distribution of defects is found to be highly nonuniform and has an inverse power-law form Nv(x)=Ax−α, where Nv(x) is the defect density at depth x measured from the surface, and A and α (≊0.6) are constants and depend on the light-soaking time. Our results show unambiguously that the Staebler–Wronski effect is a bulk effect, however the regions close to the surface are affected much more by light soaking than the regions deep in the bulk of the sample.