Phonon Spectra of (GaAs)_n(Ga_(1-x)Al_xAs)_m Superlattices According to the Keating Model

摘要

Phonon spectra of (GaAs)_n(Ga_(1-x)Al_xAs)_m superlattices were calculated using the Keating model with allowance made for long-range forces. The calculated summed longitudinal acoustical branches are consistent with observed experimental Raman doublets. The tendency towards a shift to higher frequencies of longitudinal optical modes as the number of GaAs monolayers increases, which is observed both in calculations and in experiments, is caused by localization of these modes within the GaAs layer.