Ab initio calculation of electron-phonon scattering time in germanium

The intervalley scattering time in n-type germanium from the Γ valley to the L, Δ, and X valleys, has been computed ab initio with a method based on the density functional perturbation theory. We demonstrate that the pressure dependence of the lifetime of the exciton limited by the electron-phonon interaction is well described. Moreover, we discuss relaxation times measured by various pump-probe experiments at low and ambient temperatures. The contributions of the various phonons to the scattering are computed. Relaxation times due to the electron-phonon coupling are provided for each intervalley transition, as well as their behavior under pressure.