Self-Assembled in-Plane-Gate Thin-Film Transistors Gated by WO_x Solid-State Electrolytes

Low-voltage WO_x gated indium-zinc-oxide thin-film transistors (TFTs) with in-plane-gate structures are fabricated by using an extremely simplified one-shadow mask method at room temperature. The proton conductive WO_x solid-state electrolyte is demonstrated to form an electric-double-layer (EDL) effect associated with a huge capacitance of 0.51 μF/cm². The special EDL capacitance of the WO_x electrolyte is also extended to novel in-plane-gate structure TFTs as the gate dielectric, reducing the operating voltage to 1.8 V. Such TFTs operate at n-type depletion mode with a threshold voltage of ?0.5 V, saturation electron mobility of 13.2 cm²/V?s, ON/OFF ratio of 1.7×10⁶, subthreshold swing of 110 mV/dec, and low leakage current less than 7 nA. The hysteresis window of the transfer curves is also explained by an unique reaction within the WO_x electrolyte.