Ambipolar field-effect carrier injections in organic Mott insulators

We report ambipolar field-effect characteristics observed in metal-insulator-semiconductor field-effect transistor (MISFET) device structures based on organic single crystals of the quasi-one-dimensional (Q1D) Mott-Hubbard insulator (BEDT-TTF)(F(2)TCNQ). The main aspects of the measured field-effect properties are well described by the symmetric-gate FET model, which considers the device symmetry of triode FET structures. The temperature-dependent nonlinear nature in the gated-current-voltage characteristics indicates that the ambipolar field-effect carrier injections are present down to 2 K, where the interface barrier potential between the electrode and the Mott insulator appears to be very similar for hole and electron injections, in sharp contrast to the situation involving band insulators.