Constant-photocurrent measurement and photothermal deflection spectroscopy have been used as complementary techniques to measure the density of surface states in hydrogenated amorphous silicon (a-Si:H). This method of determining surface states obviates the problem of sun-to-run variation in the sample properties encountered while measuring surface states through thickness variation. For calculations, we have taken several distributions of surface states as well as bulk states. The estimated total density of surface states is found to be insensitive to the shape of the distributions chosen. The method has been used to study the change in the density of surface states, after exposing a-Si:H to various treatments, far example light soaking, etching, and exposure to plasmas. [References: 23]
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