Shot noise suppression in multimode ballistic Fermi conductors

TL;DR

This paper derives a comprehensive formula for current noise in multimode ballistic Fermi conductors, showing how shot noise can be suppressed by Fermi correlations and space charge effects, with applications to nanoscale MOSFETs.

Contribution

It introduces a general formula for shot noise in multimode ballistic channels and demonstrates its application to a 2D nanoscale MOSFET model, highlighting noise suppression mechanisms.

Findings

Shot noise approaches Schottky value at low electron density.

Noise can be significantly suppressed at positive gate voltages.

Fermi effects mainly cause shot noise reduction.

Abstract

We have derived a general formula describing current noise in multimode ballistic channels connecting source and drain electrodes with Fermi electron gas. In particular (at $eV\gg k_{B}T$), the expression describes the nonequilibrium ''shot'' noise, which may be suppressed by both Fermi correlations and space charge screening. The general formula has been applied to an approximate model of a 2D nanoscale, ballistic MOSFET. At large negative gate voltages, when the density of electrons in the channel is small, shot noise spectral density $S_{I}(0)$ approaches the Schottky value $2eI$, where $I$ is the average current. However, at positive gate voltages, when the maximum potential energy in the channel is below the Fermi level of the electron source, the noise can be at least an order of magnitude smaller than the Schottky value, mostly due to Fermi effects.