Characterization of the hole capacitance of a hydrogenated amorphous silicon thin-film transistor

The C-V characteristics associated with hole accumulation in a-Si:H thin-film transistors (TFTs) with n⁺-type source/drain contacts were determined. The capacitance was measured by using an ac voltage and quasi-static method. In the ac measurements, we observed the partial response of the hole capacitance at low frequencies and at moderately high measurement temperatures. A full reponse of the hole capacitance was confirmed by quasi-static measurements with a long delay time at room temperature. One possible mechanism accounting for the frequency and temperature dependencies of the hole capacitance is proposed.