Evidence for field-assisted thermal emission of holes from deep mobility gap states in amorphous semiconductors from xerographic dark discharge measurements

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Abstract
The xerographic depletion discharge model describing the dark decay of the surface potential on a corona or capacitively charged amorphous semiconductor film is further developed by including an electric field enhanced charge carrier emission probability from deep mobility gap states via a Poole–Frenkel type of coulombic potential barrier lowering. An expression is derived for the dependence of the xerographic depletion time on the initial charging voltage. Xerographic dark discharge experiments carried out on vacuum‐deposited a‐Se:Te alloy photoconductor films show good agreement with the theory and indicate that the field‐assisted hole emission occurs from an exponential distribution of midgap localized states.