Energy relaxation mechanism of hot-electron ensembles in GaAs: Theoretical and experimental study of its temperature dependence

We have recently demonstrated that the fast momentum relaxation due to electron-phonon scattering of hot electrons excited into the conduction band of GaAs leads to the formation of hot-electron ensembles spread over the Brillouin zone. In the present work, we study the energy relaxation of hot-electron ensembles in GaAs, by means of ab initio calculations and time-, energy-, and momentum-resolved spectroscopy. We theoretically show that when the temperature decreases, the energy relaxation time ascribed to electron-phonon interaction becomes faster than at ambient temperature and prove that this is indeed the case in the experimental results.