Exciton-acoustic-phonon linewidths in GaAs bulk and quantum wells

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Abstract
Experimental results have shown that the acoustic phonon contribution to the homogeneous exciton linewidth increases substantially in going from GaAs quantum wells to bulk GaAs. Perturbation theory for acoustic phonon scattering using the deformation potential interaction and parabolic exciton dispersion accounts for experiment in quantum wells, but it fails by nearly an order of magnitude for bulk GaAs. Here we develop a theory of exciton-acoustic-phonon homogeneous linewidths using the anisotropic exciton dispersion, and we find for bulk GaAs that the piezoelectric interaction dominates the scattering. These results show that perturbation theory including these effects accounts well for the low temperature exciton linewidth in bulk GaAs as well as that in GaAs quantum wells. This approach also accounts for the available experimental results for exciton linewidths in bulk ZnSe and in ZeSe quantum wells.