The dark current‐voltage characteristics ofp‐i‐nhydrogenated amorphous silicon diodes with various thicknesses of the intrinsic layer (i‐layer) (770–9300 A˚) are systematically investigated. The magnitude of the forward current is found to be independent of thickness of theilayer, which is obviously against the simple conventional junction theory. It has been demonstrated through various experiments that the forward current of amorphousp‐i‐ndiodes is limited by a layer thinner than 770 A˚, possibly being thep/iinterface or a narrow zone of theilayer.