The leakage currents of amorphous silicon thin-film transistors: channel charge emission

The effects of channel charge emission on the transient leakage currents of amorphous silicon thin-film transistors are described. Up to one hundred devices connected in parallel are used to allow measurement of currents below 1 fA. We develop a procedure to separate the charge-emmission current from the injection and generation currents, based on the dependence on the drain-to-source voltage. The channel emission current is isolated and measured from 10^-3 to 100 s after the TFT is switched off. The current decays approximately as 1/t, and provides information about the density of states in a-Si:H. The channel charge emission also influences the read-out properties of active matrix arrays.