Electric potential and threshold voltage models for double-gate Schottky-barrier source/drain MOSFETs

The threshold voltage, Vth of a double-gate (DG) Schottky-barrier (SB) source/drain (S/D) metal-oxide-semiconductor field-effect transistor (MOSFET) has been investigated. An analytic expression for surface potential is obtained by using Gauss's law and solving Poisson's equation, the results of which are compared with simulations, and good agreement is observed. Based on the potential model, a new definition for Vth is developed, and an analytic expression for Vth is obtained, including quantum mechanical effects and SB lowering effect. We find that Vth is very sensitive to the silicon body thickness, tsi. For a device with a small tsi (<3 nm), Vth increases dramatically with the reduction of tsi. Vth decreases with the increase of the back-gate oxide thickness, and with the increasing of the drain bias. All the results can be of great help to the ultra-large scale integrated-circuit (ULSI) designers.

► Definition for threshold voltage of device is developed, with quantum mechanical effects, Schottky-barrier lowering effect.
► An analytic expression for threshold voltage is obtained, the expression can be great help to integrated circuit designers.
► Some properties of the threshold voltage of the transistor are demonstrated.