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

Abstract

High-field charge transport in semiconductors is of fundamental interest and practical importance. While the 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 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, indicating that off-shell 2ph or other processes play a fundamental role in high-field transport. This observation highlights how ab initio calculations of PSD may be used as a stringent test of the electron-phonon interaction in semiconductors.

High-field charge transport and noise in p -Si from first principles

“…The details of the method used in this work have been described previously [27,28]. In summary, high-field transport and noise properties are calculated by solving the Boltzmann transport equation with the electronic states, phonon dispersion, and electron-phonon collision matrix computed from first principles.…”

“…The numerical methods are identical to those in Refs. [27,28]. The calculation of electronic structure and electron-phonon matrix elements are performed with Quantum Espresso [68,69] using a coarse 8×8×8 grid, wave function energy cutoff of 60 Ryd, and a lattice constant of 5.430 Å.…”

“…Recent works have extended this method to study high-field transport phenomena and noise [27][28][29]. High-field transport calculations offer a stricter test of the theory because band anisotropy, intervalley and interband scattering, and energy relaxation take on increased importance [30][31][32][33].…”

“…Additionally, the full solution to the BTE is necessary at high fields [27,67]. Recent methods for the ab-initio treatment of high-field transport [27][28][29] have not yet been applied to p-type semiconductors.…”