Transition from longitudinal-optical phonon scattering to surface-optical phonon scattering in polar semiconductor superlattices

Dielectric continuum models of optical-phonon modes predict an enhancement in the strength of the surface-optical (SO) modes in double-barrier heterostructures as the heterojunction-to-heterojunction separation is reduced. There is currently no consensus on the nature of the electron-SO-phonon coupling interaction. In this work, the ratio of electron scattering by the SO-phonon modes to that by the confined longitudinal-optical (LO) phonon modes is calculated for a GaAs/AlAs short-period superlattice based on the assumption that the electron-SO-phonon interaction 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.