Electron-phonon coupling in semiconductors at high electronic temperatures

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 $\ensuremath{\sim}25000\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. 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 potentials 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 $\ensuremath{\sim}35%$ from its equilibrium counterpart for identical deposited energy density, allowing us 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, $\mathrm{Ti}{\mathrm{O}}_{2}, {\mathrm{Cu}}_{2}\mathrm{O}$; layered $\mathrm{Pb}{\mathrm{I}}_{2}$; ZnS and ${\mathrm{B}}_{4}\mathrm{C}$.