Effect of Phonon Scattering on Intrinsic Delay and Cut-Off Frequency of Carbon Nanotube FETs

TL;DR

This paper investigates how phonon scattering impacts the intrinsic delay and cut-off frequency of carbon nanotube FETs, revealing that scattering causes charge pile-up and degrades high-frequency performance.

Contribution

It provides a detailed quantum-mechanical analysis of phonon scattering effects on CNTFET performance, highlighting the impact on delay and frequency response.

Findings

Charge pile-up increases delay and capacitance.

Phonon scattering reduces cut-off frequency.

DC on-current is minimally affected.

Abstract

The effect of phonon scattering on the intrinsic delay and cut-off frequency of Schottky barrier carbon nanotube (CNT) FETs is examined by self-consistently solving the Poisson equation and the Schrodinger equation using the non-equilibrium Greens function (NEGF) formalism. Carriers are mostly scattered by optical and zone boundary phonons beyond the beginning of the channel. We show that the scattering has a small direct effect on the DC on-current of the CNTFET, but it results in significant pile-up of charge and degradation of average carrier velocity. Due to charge pile-up and random walks of carriers, the intrinsic gate capacitance and delay significantly increase, and the intrinsic cut-off frequency decreases. The results are important for assessing the performance potential of CNTFETs for radio-frequency (RF) electronics and digital electronics applications.