REVERSE CURRENT MECHANISMS IN AMORPHOUS-SILICON DIODES

We analyze the dark steady-state reverse current of a-Si:H nip diodes at high voltages. The reverse current shows a strong voltage dependenc e and has a temperature dependence characterized by a voltage-dependen t activation energy. A model, based on the simultaneous field enhanced generation of electrons and holes, is developed to describe this volt age and temperature dependence. In this model the effective mass of el ectrons and holes is a model parameter. Good fits with experimental re sults are obtained for an effective mass value of 0.05m(e). The low ef fective mass value is tentatively explained as a parameter that accoun ts for a field dependent narrowing of the band gap due to the presence of localized band tail states.