High-field transport and hot electron noise in GaAs from first principles: role of two-phonon scattering

TL;DR

This paper presents a first-principles calculation of high-field electron transport and noise in GaAs, highlighting the significant role of two-phonon scattering in accurately modeling intervalley processes and relaxation dynamics.

Contribution

It introduces the first extit{ab initio} approach to include on-shell two-phonon scattering in high-field transport modeling of GaAs, resolving previous discrepancies in intervalley scattering strength.

Findings

Two-phonon scattering significantly affects high-field electron distribution.

Intervalley scattering rates are increased by two-phonon processes.

The non-monotonic PSD trend with electric field is not captured at this level.

Abstract

High-field charge transport in semiconductors is of fundamental interest and practical importance. While the \textit{ab initio} treatment of low-field transport is well-developed, the treatment of high-field transport is much less so, particularly for multi-phonon processes that are reported to be relevant in GaAs. Here, we report a calculation of the high-field transport properties and current power spectral density (PSD) of hot electrons in GaAs from first principles including on-shell two-phonon (2ph) scattering. The on-shell 2ph scattering rates are found to qualitatively alter the high-field distribution function by increasing both the momentum and energy relaxation rates as well as contributing markedly to intervalley scattering. This finding reconciles a long-standing discrepancy regarding the strength of intervalley scattering in GaAs as inferred from transport and optical studies. The characteristic non-monotonic trend of PSD with electric field is not predicted at this level of theory. Our work shows how \textit{ab initio} calculations of high-field transport and noise may be used as a stringent test of the electron-phonon interaction in semiconductors.