Raman scattering by folded longitudinal acoustic phonons in InAs/GaSb superlattices - Resonant enhancement an effect of interfacial bonding

We have studied backfolded longitudinal acoustic (LA) phonons in InAs/GaSb superlattices (SLs) intentionally grown with either InSb-like or GaAs-like interfaces (IFs). Raman scattering by folded LA phonons was found to be resonantly enhanced for incident photon energies slightly below the 2.0 eV electronic SL interband transition, observed previously by spectroscopic ellipsometry and by resonant Raman scattering from longitudinal optical SL phonons. Under resonant excitation, InAs/GaSb SLs with InSb-like IFs showed scattering by folded LA phonons up to the 7th order. For SLs with GaAs-like IFs, the folded LA phonon modes occurred at systematically higher frequencies than for SLs with the same nominal period and InSb-like IFs. The difference in frequency increased with decreasing SL period.