Phonon and plasmon deformation potentials of GaAs: Far-infrared study under uniaxial stress

We report the results of a complete study of the effects of a uniaxial stress on the far-infrared reflectivity spectrum of GaAs. Stresses up to 15 kbar applied along the [111] and [001] directions allowed us to measure splittings of phonon degeneracies and frequency shifts of the long-wavelength TO and LO phonons and of the free-carrier plasma frequency. From these results we were able to calculate the phonon and plasmon deformation potentials. More importantly, numerical values are obtained for the rate of shifts of the electron effective mass. The results are compared with values given in the literature.