Pressure-induced resonance broadening of exciton line shapes in semiconductors: Direct determination of intervalley scattering rates in GaAs

We show that the exciton photoluminescence line shape in the GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells under pressure is broadened by hybridization of the Γ exciton with the X and the L continua via electron-phonon coupling. Furthermore, we demonstrate the pressure tuning of the resonance-broadening effect which can be used to extract the electron-phonon coupling parameters directly. For GaAs we estimate the intervalley electron-phonon deformation potential ${\mathit{D}}_{\mathrm{\Gamma }\mathit{X}}$ to be 10.7±0.7 eV/Å. The resonance effect should be observable in other semiconductors as well.