Density-of-states and transient simulations of amorphous-silicon devices

We present two-dimensional numerical simulations and experimental data of the transient behavior of amorphous-silicon devices. In general, experiments show that the filling of traps in amorphous silicon is a relatively fast process whereas the slow release of carriers from the trapped state produces long tails in a device's transient characteristics. In this paper we show good agreement between experimental data and numerical simulations of the transient response of both diodes and thin-film transistors. Our two-dimensional numerical model solves the complete set of transport equations in amorphous silicon, fully accounting for the traps in the mobility gap. These traps are assumed to obey Shockley-Read-Hall kinetics. Our program self-consistently calculates the occupation functions for both acceptor and donor-like states with respect to position, energy, and time.