Transition from LO-phonon to SO-phonon scattering in mesoscale structures

Macroscopic dielectric continuum models of optical-phonon modes predict enhancements in the magnitudes of the surface-optical (SO) modes in double-barrier heterostructures as the heterojunction-to-heterojunction separation is reduced. In this paper, the ratio of electron scattering by the SO-phonon modes to that by the (electrostatic) confined longitudinal-optical- (LO-) phonon modes is calculated for a GaAs/AlAs short-period superlattice based on the assumption that electron-SO-phonon scattering may be described by a scalar potential. The scaling of the ratio of electron-SO-phonon scattering to electron-LO-phonon scattering as a function of the superlattice period provides a sensitive test of the appropriateness of the scalar-potential model. The effect of phonon confinement on electron-optical-phonon scattering rates is presented for rectangular quantum wires as well. A major conclusion of these new results is that it is essential to model phonon confinement properly in predicting carrier transport properties in mesoscale structures.