Modeling of accumulation-mode MOSFET´s in PolySilicon thin films

An analytic model of p-channel polysilicon MOSFET operating in accumulation mode is presented. The measured device transfer characteristics, for passivated and unpassivated films, are quantitatively explained in terms of leakage, subthreshold, and drive regimes of operation. The observed current swing of 10⁴is shown to result primarily from the gate-voltage-induced mobility enhancement. This enhancement, a unique feature of polysilicon, is quantified via electrostatic shielding and barrier-potential-dependent mobility. The model describes transconductance, drain admittance, and ON/OFF ratio as a function of grain size, trap density and level, film thickness, and doping concentration.