Transfer of excess charge carriers in an a-Si:H/crystalline-silicon heterojunction measured during the growth of the amorphous silicon layer

The plasma-induced deposition of hydrogenated amorphous silicon on crystalline silicon substrates has been investigated in situ by contactless transient photoconductivity measurements. In the initial stage of the deposition process the signals reflect charge-carrier kinetics in the substrate with the surface recombination rate modified by the deposition process. In the final stage the signal is dominated by mobile electrons in the film deposited. Between these extrema an additional contribution of excess charge carriers optically induced in the amorphous silicon film and transported to the substrate is observed. It is shown that this transport is inhibited by a high defect density in the film deposited and by a highly defective interface