1e:T4bd, Through mixed-mode device and circuit simulation, this paper provides an estimate of the effective output capacitance $(C_{\rm EFF})$ and drive current $(I_{\rm EFF})$ for delay ($ \tau_{f} = \hbox{0.69} R_{\rm sw}C_{\rm EFF}$, where $R_{\rm sw} = V_{\rm DD}/\hbox{2}\ I_{\rm EFF}$) estimation of unloaded tunnel field-effect transistor (TFET) inverters. It is shown that unlike MOSFET inverters, where $C_{\rm EFF}$ is approximately equal to the gate capacitance $(C_{\rm gg})$ , in TFET inverters, the output capacitance can be as high as 2.6 times the gate capacitance. A three-point model is proposed to extract the effective drive current from the real-time switching current trajectory in a TFET inverter. 1f:T43f,In this brief, a novel U-shape-channel tunneling field-effect transistor (UTFET) with a SiGe source region is investigated by 2-D technology computer aided design simulation. The enlarged tunneling area and enhanced tunneling rate dramatically increase the tunneling current when the device is turned on. Meanwhile, the off-leakage current of UTFET is suppressed because of the extended physical channel length. The on-state tunneling current of UTFET can be further improved by introducing an n ⁺ -doped Si delta layer under the source region. The inserted delta layer significantly shortens the band-to-band tunneling path, enlarges tunneling area, and thus enhances the tunneling rate of this device. The average value of the subthreshold swing (SS) of the optimized UTFET is 58 mV/dec when VGS is varied from 0 to 0.46 V. Using the SiGe-source UTFET structure with a delta layer, the merits of low leakage current, high drive current, and ultralow SS can be realized simultaneously.

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