Drive-level capacitance profiling: Its application to determining gap state densities in hydrogenated amorphous silicon films

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Abstract
We have developed a new method of capacitance profiling which is greatly superior to standard profiling techniques for materials like amorphous silicon that contain high densities of deep gap states. This technique, which makes use of the variation of the junction capacitance with the alternating voltage amplitude, is largely immune to the effects of surface states and is readily interpreted in terms of a simple integral over the density of states,g(E). This method is applicable to both doped and semi‐insulating undoped samples.