Steep subthreshold slope nanowire nanoelectromechanical field-effect transistors (NW-NEMFETs)

Significant physical challenges remain for CMOS technology to decrease I
_off
as transistor dimension and power supply voltages continue downscaling. However, a fundamental thermodynamic limit in the subthreshold slope SS = |(∂V
_g
)/(∂lnI
_d
)| = ln10 · k
_B
T/q at >60 mV/dec exists at room temperature. We have designed and demonstrated the first semiconductor nanowires (NWs) and nanoelectromechanical system (NEMS) field effect transistor structure (NW-NEMFET). We have previously demonstrated 0.5 ps intrinsic delay and near ballistic operation in quantum confined semiconductor heterostructure NWFETs with diameters less than 15 nm.[1] The current design uses high performance suspended semiconductor NWs as the conduction channel, while the electrostatic pull-in of the NW towards the gate stack enables abrupt switching to the off-state leading to high frequency, low power nanoelectronics. Simulation shows that compared to planar suspended-gate FET (SGFET) design [2], NW-NEMFET allows zero SS with 10
¹⁵
on-off ratio and near 1V pull-in voltage due to enhanced 3D capacitive coupling, as well as operation at very-high-frequency (VHF) and even ultra-high-frequency (UHF) due to the NW beams high aspect ratio and small dimensions.