Electron-phonon coupling in semiconductors at high electronic temperatures

TL;DR

This study uses a nonperturbative dynamical approach to evaluate electron-phonon coupling in irradiated semiconductors at high electronic temperatures, comparing equilibrium and nonequilibrium models across 14 materials.

Contribution

It introduces a method that accounts for arbitrary electronic distributions to accurately evaluate electron-phonon coupling at high temperatures in semiconductors.

Findings

Nonequilibrium effects alter coupling by up to 35% compared to equilibrium.

The coupling parameter can be approximated as a function of electronic temperature.

14 different semiconductors were systematically analyzed.

Abstract

A nonperturbative dynamical coupling approach based on tight-binding molecular dynamics is used to evaluate the electron-ion (electron-phonon) coupling parameter in irradiated semiconductors as a function of the electronic temperature up to ~25,000 K. The method accounts for arbitrary electronic distribution function via the Boltzmann equation, enabling a comparative analysis of various models: fully equilibrium electronic distribution, band-resolved local equilibria (distinct temperatures and chemical potential of electrons in the valence and the conduction band), and a full nonequilibrium distribution. It is demonstrated that the nonequilibrium produces the electron-phonon coupling parameter different by at most ~35% from its equilibrium counterpart for identical deposited energy density, allowing to use the coupling parameter as a function of the single electronic equivalent (or kinetic) temperature. The following 14 semiconductors are studied here - group IV: Si, Ge, SiC; group III-V: AlAs, AlP, GaP, GaAs, GaSb; oxides: ZnO, TiO2, Cu2O; layered PbI2; ZnS and B4C.