Electron-Electron Interactions in Device Simulation via Non-equilibrium Green's Functions and the GW Approximation

TL;DR

This paper introduces an  ab initio simulation framework combining density functional theory, non-equilibrium Green's functions, and the GW approximation to accurately model electron-electron interactions in ultra-scaled MOSFETs, revealing their impact on device behavior.

Contribution

It presents the first large-scale atomistic quantum transport simulation of nano-devices incorporating non-equilibrium e-e interactions via the GW approximation.

Findings

E-e interactions significantly alter carrier and current distributions.

On-current decreases due to Coulomb repulsion.

Bandgap modulation can enhance device performance.

Abstract

The continuous scaling of metal-oxide-semiconductor field-effect transistors (MOSFETs) has led to device geometries where charged carriers are increasingly confined to ever smaller channel cross sections. This development is associated with reduced screening of long-range Coulomb interactions. To accurately predict the behavior of such ultra-scaled devices, electron-electron (e-e) interactions must be explicitly incorporated in their quantum transport simulation. In this paper, we present an \textit{ab initio} atomistic simulation framework based on density functional theory, the non-equilibrium Green's function formalism, and the self-consistent GW approximation to perform this task. The implemented method is first validated with a carbon nanotube test structure before being applied to calculate the transfer characteristics of a silicon nanowire MOSFET in a gate-all-around configuration. As a consequence of e-e scattering, the energy and spatial distribution of the carrier and current densities both significantly change, while the on-current of the transistor decreases owing to the Coulomb repulsion between the electrons. Furthermore, we demonstrate how the resulting bandgap modulation of the nanowire channel as a function of the gate-to-source voltage could potentially improve the device performance. To the best of our knowledge, this study is the first one reporting large-scale atomistic quantum transport simulations of nano-devices under non-equilibrium conditions and in the presence of e-e interactions within the GW approximation.