Ab initio study of Γ-X intervalley scattering in GaAs under pressure

State-of-the-art ab initio methods have been used to describe the evolution of the Γ-X intervalley scattering deformation potential (IDP) in gallium arsenide under pressure. We show that both our IDP dispersion and its pressure dependence lead to a decrease of the scattering within the first conduction band. DΓX =4.2 eVÅ is our theoretical value of the average IDP for transitions at the direct-to-indirect band gap crossover pressure. We estimate the theoretical average IDP to be 3.8 eVÅ at the pressure where Γ-L scattering becomes allowed. We propose a model beyond Conwell's one that includes the pressure dependence of the IDP, which we have applied to the broadening of the excitonic line under pressure. Fitting the experimental results of Goñi [Phys. Rev. B 41, 10111 (1990)] to our model, we found a satisfactory agreement between the experimental IDP and our theoretical values.