Ab initio study of electron–phonon coupling and excitonic linewidth in GaAs under pressure and in GaP

Interactions between excited electrons and short-wavelength (intervalley) phonons are the major source for the broadening of the excitonic line in GaAs under pressure and in GaP. We have studied the intervalley scattering deformation potential using density functional theory for the conduction bands, and density functional perturbation theory for phonon frequencies and for the matrix elements of the electron–phonon interaction. We have calculated the electron–phonon scattering time due to intervalley scattering image, integrating the scattering probabilities over all possible final states in the Brillouin zone without any ad hoc assumption about the behavior of the electron–phonon matrix elements nor the topology of the conduction band. We compare our theoretical results with time-resolved photoluminescence experiment in GaAs, and with spectroellipsometry measurements in GaAs under pressure and in GaP. We show that our ab initio method also allows the evaluation of effective deformation potentials.