First-principles study of high-field charge transport and fluctuations in n-GaAs

First-principles calculations of charge transport properties in semiconductors are now routine but typically restricted to low field, linear response properties such as mobility. On the other hand, the power spectral density (PSD) is known to be sensitive to the precise electron-phonon interactions occurring in the material and is readily experimentally accessible, yet few ab-initio calculations of this quantity have been reported. Here, we report an ab-initio calculation of both high field transport properties and power spectral density (PSD) of hot electrons in GaAs. We find that although qualitative agreement is observed for the high-field drift velocity characteristics, the agreement with the PSD is poor. The agreement for the drift velocity is improved with inclusion of on-shell two-phonon processes but fails to improve the agreement with the PSD. Our work suggests that additional scattering processes are of fundamental importance to explain the PSD trend with electric field in GaAs. Further, our work illustrates the use of PSD to probe the electron-phonon interaction in semiconductors.