Amorphous silicon device simulation by an adapted Gummel method

The operation of hydrogenated amorphous silicon devices depends crucially on the interplay between the dynamics of free and trapped carriers. This is due to a density of acceptor and donor states present in the mobility gap of amorphous materials. It is shown that Gummel's method used for the simulation of crystalline-material-based devices has to be modified to account for this interplay. The midgap density of states is identified as the parameter controlling the nature of the dynamics of the carriers and this is illustrated with two examples: the 1D Schottky diode and the 2D static induction transistor