Dynamic Characteristics of Amorphous Silicon Thin Film Transistors

In this paper we report on the dynamic characteristics of amorphous silicon thin film transistors in the time interval between ips to 1s after gate switch-on. The experimental results show a continuous change in the threshold voltage in this t’me regime. A model based on carrier thermalisation to the deep states including the spatial dependence of the thermalisation process in the band-banding region is presented to account for these results. The effect responsible for the observed time dependence of the threshold voltage is shown to be the trapping of charge in deep states in the bulk amorphous silicon away from the interface with the gate dielectric.