The reversal of drifting excess carriers in an amorphous silicon junction

Abstract

The ‘crucial’ experiment recently described by Silver et al. in which the electric field applied to an a-Si junction was reversed during the drift of a pulse of excess electrons has been repeated. It is demonstrated that, contrary to the previous results, reversal leads to an electron flow in the opposite direction. Furthermore, the charge in the reversed signal is equal to that displaced in the original drift pulse up to the time of reversal, provided that the latter lies within the transit time. It is concluded that the interpretation of Silver et al. cannot be upheld and that the pulses normally observed in drift mobility experiments on a-Si represent the transit of excess carriers.