Three-terminal capacitance–voltage measurements of pentacene field-effect transistors during operation

•A modified technique of capacitance measurement for transistors was proposed.•The technique enables to observe the channel formation processes of transistors.•The channel formation processes of pentacene transistors were observed.•Validity of the gradual channel approximation in pentacene transistors was examined.

We propose a modified measurement technique of capacitance for three-terminal devices and apply this method for the evaluation of the channel formation in pentacene field-effect transistors. An additional structure in the capacitance–voltage curves clearly shows the channel formation from the saturation to the linear region in an operating transistor which has not been directly observed in conventional methods. Based on the amount of accumulated charge in the channel region, the validity of the gradual channel approximation model and the usability of a buffer layer are discussed. This method enables the detailed investigation of carrier behaviors in organic transistors through appropriate evaluation of the channel formation process during operation.

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