Simulation of phonon-assisted band-to-band tunneling in carbon nanotube field-effect transistors

TL;DR

This paper models phonon-assisted band-to-band tunneling in carbon nanotube FETs using non-equilibrium Green's functions, revealing how phonon scattering influences ambipolar conduction and subthreshold swing.

Contribution

It introduces a detailed simulation approach incorporating electron-phonon interactions to analyze tunneling and ambipolar conduction in CNT FETs.

Findings

Phonon scattering shifts ambipolar conduction onset to higher gate voltages.

Subthreshold swing as steep as 40 mV/decade is achievable despite phonon effects.

Phonon-assisted tunneling significantly impacts CNT FET performance.

Abstract

Electronic transport in a carbon nanotube (CNT) metal-oxide-semiconductor field effect transistor (MOSFET) is simulated using the non-equilibrium Green's functions method with the account of electron-phonon scattering. For MOSFETs, ambipolar conduction is explained via phonon-assisted band-to-band (Landau-Zener) tunneling. In comparison to the ballistic case, we show that the phonon scattering shifts the onset of ambipolar conduction to more positive gate voltage (thereby increasing the off current). It is found that the subthreshold swing in ambipolar conduction can be made as steep as 40mV/decade despite the effect of phonon scattering.