Optical absorption spectra of surface or interface states in hydrogenated amorphous silicon

Abstract

The optical absorption of doped and undoped hydrogenated amorphous silicon (a-Si:H) films ranging from 5 nm to 10 μm was measured using photothermal deflection spectroscopy. The absorption spectra show that there is a high defect layer associated with the surface or interface of the film. From comparison of defect absorption and dangling bond spin densities, it is found that a-Si:H films which have ∼1015 bulk defects/cm3 exhibit surface or interface layers with ∼1012 dangling bonds/cm2.