Interference effects in acoustic-phonon Raman scattering from GaAs/AlAs mirror-plane superlattices

Raman scattering of longitudinal-acoustic phonons has been studied in finite-size mirror-plane superlattices (MPSL's) with building blocks SL=(GaAs${)}_{13}$/(AlAs${)}_{18}$ and LS=(AlAs${)}_{18}$/(GaAs${)}_{13}$, arranged to form layer sequences (SL${)}_{\mathrm{m}\mathrm{/}2}$/(LS${)}_{\mathrm{m}\mathrm{/}2}$ with different numbers of building blocks m. In contrast to periodic structures (SL${)}_{\mathrm{m}}$, the folded LA-phonon doublets in MPSL's experience pronounced splittings, while satellites appear around the main lines. These effects are due to the interference of the scattering contributions from the different quantum wells in the sample, and reflect a phase shift introduced by the mirror-plane symmetry. This phase shift can be tuned by GaAs buffers of different widths in structures of the type (SL${)}_{\mathrm{m}\mathrm{/}2}$/ (GaAs${)}_{\mathrm{n}}$/(LS${)}_{\mathrm{m}\mathrm{/}2}$.