Electric Double Layer Transistor of Organic Semiconductor Crystals in a Four-Probe Configuration

Electric double layer field-effect transistors (EDL-FETs) of rubrene single crystals using a liquid polymer electrolyte were studied in a four-probe configuration. The channel sheet resistance and the contact resistance normalized by the contact width were 0.24 MΩ and 0.83 kΩ cm in the ON-state, respectively. These values are smaller than those of previously reported conventional rubrene crystal FETs, corroborating the high carrier density accumulation in the EDL-FET. In addition, peculiar peak behaviour in the transfer characteristics did not appear in the gate voltage dependence of four-probe conductivity. This observation leads us to conclude that the peak is ascribed to the increase of the contact resistance in the high gate voltage region.