NbO2 based threshold switch device with high operating temperature (>85°C) for steep-slope MOSFET (∼2mV/dec) with ultra-low voltage operation and improved delay time

Abstract

To realize a steep slope field-effect transistor (FET) with low leakage current and controllable operating bias, NbO2 threshold switching (TS) device is connected in series with the gate side of a MOSFET. Thanks to the TS device showing abrupt transition between the OFF and ON states at threshold voltage (Vth), the implemented transistor exhibits extremely low leakage current (10⁻⁷μA/μm), high Ion/Ioff ratio (>10⁶), sub-2 mV/dec subthreshold swing, drift-free characteristic and high temperature operation (>85°C). Furthermore, since the Vth is tunable by controlling thickness of the NbO2 TS device, the new NbO2-MOSFET can fulfill various demands of operating bias conditions. In addition, we confirmed through a simulation that the CMOS inverter with NbO2 connected to the gate side showed fast inverting speed of over 300 MHz at ultra-low voltage (<0.3V), improved propagation delay time by x3.0 and reduced operation Vd (ΔV>200mV).