Wannier interpolation of the electron-phonon matrix elements in polar semiconductors: Polar-optical coupling in GaAs

Abstract

We generalize the Wannier interpolation of the electron-phonon matrix elements to the case of polar-optical coupling in polar semiconductors. We verify our methodological developments against experiments, by calculating the widths of the electronic bands due to electron-phonon scattering in GaAs, the prototype polar semiconductor. The calculated widths are then used to estimate the broadenings of excitons at critical points in GaAs and the electron-phonon relaxation times of hot electrons. Our findings are in good agreement with available experimental data. Finally, we demonstrate that while the Fröhlich interaction is the dominant scattering process for electrons/holes close to the valley minima, in agreement with low-field transport results, at higher energies, the intervalley scattering dominates the relaxation dynamics of hot electrons or holes. The capability of interpolating the polar-optical coupling opens new perspectives in the calculation of optical absorption and transport properties in semiconductors and thermoelectrics.

First-principles calculations of thermal, electrical, and thermoelectric transport properties of semiconductors

“…Wannier interpolation scheme by using a rigid ion model to treat the long-range effect, where each atom carries certain effective charge due to their ionic character and the polar scattering mainly comes from the Coulomb interaction between them and the electrons [51,52]. The interpolated electron-phonon matrix elements agree well with those obtained from direct DFPT calculations [51,52].…”

“…The interpolated electron-phonon matrix elements agree well with those obtained from direct DFPT calculations [51,52]. We believe the inclusion of the polar scattering will facilitate the study of the electrical transport of more complicated semiconductors and provide more possibilities for engineering material's electrical property.…”

“…For these materials, these long range forces need to be separately treated, as what has been done for the LO-TO splitting in the phonon dispersion calculation using DFPT [19,49,49]. Recently these long-range effects have been incorporated into the Wannier interpolation scheme by using a rigid ion model (assigning effective charges to each atom and consider their Coulomb interactions with electrons) [50] to approximate the electron-phonon matrix element for long-wavelength LO phonons [51,52]. This development thus further extends the efficient computation of electron-phonon couplings towards polar semiconductors.…”

Ab initiostudy of cross-interface electron-phonon couplings in FeSe thin films onSrTiO3andBaTiO3

“…39,40,51 For example, by proposing a charge depletion region across multiple unit cells in the STO substrate near the interface, Zhou et al 52 obtained from calculations a much larger total coupling strength λ ∼ 0.4 to the topmost oxygen phonon branch, which is peaked at small q. Furthermore, the exact structure of the terminating layer of the substrate has yet to be determined.…”

“…Note, however, that none of the interpolation techniques mentioned above can properly treat the matrix elements with long spatial decay in real space, or with a sharp peak near q = 0 in momentum space. 39,40 This is most likely to be the case where the q = 0 weight is not negligible. We will come back to this comment again below.…”