Transient Leakage Currents in Amorphous Silicon Thin-Film Transistors

In this paper we present both experimental data and computer simulations of the leakage characteristics of amorphous silicon (a-Si) thin film transistors operated under time transient conditions. The transient behaviour of these devices for realistic operating conditions is often very different from their steady-state characteristics, due to the slow response of deep traps in a-Si. Our model is in good agreement with the data and realistically accounts for the time-dependent behaviour of amorphous silicon with leakage being mainly determined by a combination of fixed charge in the passivation dielectric and a distribution of surface states at the top silicon interface. We show how voltage pulses applied to the gate of a TFT affect its performance as a pixel switch in a two-dimensional array. In particular we concentrate on the effects of light and bias stressing.