Intrinsic capacitance of amorphous silicon and polysilicon thin film transistors

Results on the capacitance of thin-film transistors (TFTs) as a function of gate and drain voltage are shown. Measurements of amorphous silicon (a-Si) TFTs are in good agreement with a model based on the gradual channel approximation, accounting for the a-Si density of states. This model has been used with the circuit simulator SPICE. For polysilicon TFTs the measurements show two effects, an increase in the transistor's capacitance due to the leakage current at negative gate bias and a rise due to the injected current from the kink effect.<>