COMPACT CAPACITANCE MODEL FOR PRINTED THIN FILM TRANSISTORS WITH NON-IDEAL CONTACTS

We report on a compact capacitance model that accurately describes both the gate length dependent and the gate length independent frequency dispersion observed in C-V curves for printed thin film transistors with non-ideal contacts. We also show that modeling the drain current with two adjacent subthreshold regions (instead of just one in the previous RPI TFT model) is needed to match the measured current-voltage characteristics. We show that Elmore model which accounts for channel length transit time is not sufficient for describing the frequency dispersion in C-V curves for printed TFTs and present the new Variable Dispersion Model (VDM). VDM reproduces the experimentally observed gate length independent dispersion arising due to the finite time of the electron exchange between the localized states in the mobility gap and the states above the mobility edge in amorphous semiconductors. The combined Elmore-VDM model has been implemented in AIM-Spice and showed good agreement with measured C-V data.