Channel Pinchoff Near Drain in Top Contact Organic Thin-Film Transistor

An investigation of channel pinchoff close to the drain electrode in a top contact organic thin-film transistor is described using a technique that uses a floating electrode to sense the voltage at the edge of the drain electrode. Upon sweep of the drain voltage from zero to a value larger than saturation voltage, the floating probe tracks the drain voltage until the accumulation layer in the channel is pinched off causing it to be disconnected from the drain. The voltage to which the floating probe gets stuck is equal to the pinchoff voltage of the transistor. Results from 2-D numerical simulation of a transistor are presented to validate the principle of the proposed approach and the experimental results obtained with pentacene transistors are presented to highlight the insight offered by it.