Origin of electric field distribution in organic field-effect transistor: Experiment and analysis

Electric field distribution in the pentacene organic field-effect transistor (OFET) channel is investigated using the microscopic optical second-harmonic generation (SHG). At the on- and off-states of the OFET, enhanced SHG signal was observed near the drain electrode and at the source and drain electrodes. Our analytical analysis indicates that the Laplace field formation is in the off-state of the OFET. The electric field profile in the on-state representing distribution by the space-charge formation in the channel due to injected carriers was calculated by the transmission line model. Theoretical models are confirmed by the experimental results and the result shows that pentacene can be used as a dielectric material. On the basis of estimated potential distribution in the on-state, a model for the evaluation of the drain-source current is proposed.