Investigation of Light-Induced Defect Depth Profile in Hydrogenated Amorphous Silicon Films

ABSTRACTWe report direct measurement of depth profile of light induced defects (LIDs) in hydrogenated amorphous silicon (a-Si:H) films. These depth profiles were measured by ESR measurements combined with layer-by-layer precise wet etching technique. We discuss those LIDs depth profiles in relation to the spatial depth distribution of photocarriers generation and recombination profiles, as well as the defect creation efficiency. In case of uniformly absorbed light, the light induced defects creation takes place uniformly in depth of the a-Si:H film. In case of nonuniformly absorbed light, the LIDs depth profile is spatially wider than photocarrier generation rate profile G(x), and depends on G(x) sublinearly. Moreover, the LID depth profile agrees well with the photocarrier direct recombination rate profile rather than the profile of total recombination rate or that through defects. The obtained results suggest that the LIDs creation takes place at local site where the photocarriers recombine directly.