AC Analysis of Amorphous-Silicon Structures

A generalized version of the small-signal drift-diffusion model accounting for trapped charge dynamics is presented; the explicit introduction of two new continuity equations for the trapped electrons and holes is avoided by incorporating them in the original three equations, thus allowing for easier implementation while mantaining the same degree of accuracy of the full system. Simulations carried out on a MOS device result in a good agreement between simulated and measured inter-electrode capacitances. Finally, the dependence of the gate-to source and gate-to-drain capacitances on both bias and frequency is discussed.