DFT modelling of bulk-modulated carbon nanotube field-effect transistors

TL;DR

This paper uses density-functional theory and non-equilibrium Green's functions to simulate and analyze the transport properties of bulk-modulated carbon nanotube FETs, revealing key physical mechanisms and performance limits.

Contribution

It provides an atomistic understanding of transport in bulk-modulated CNTFETs, highlighting the effects of one-dimensional screening and quantum capacitance on device performance.

Findings

One-dimensional screening significantly influences current modulation.

Correct evaluation of nanotube quantum capacitance is crucial.

Short channel effects impact device operation and limits.

Abstract

We report density-functional theory (DFT), atomistic simulations of the non-equilibrium transport properties of carbon nanotube (CNT) field-effect transistors (FETs). Results have been obtained within a self-consistent approach based on the non-equilibrium Green's functions (NEGF) scheme. Our attention has been focused on a new kind of devices, the so called bulk-modulated CNTFETs. Recent experimental realizations \cite{Chen,Lin_condMat} have shown that such devices can exhibit excellent performances, even better than state-of-the-art Schottky barrier (SB)-modulated transistors. Our calculations have been intended to explore, at an atomistic level, the physical mechanisms governing the transport in these new devices. We emphasize the role that one-dimensional screening has on gate- and drain-induced current modulation mechanisms, pointing out, at the same time, the importance of a correct evaluation of the nanotube quantum capacitance. The operative regimes and the performance limits of the device are analysed, pointing out, at the same time, the role played by the quasi-one-dimensional, short channel effects.