Lattice vibration modes in type-II superlattice InAs/GaSb with no-common-atom interface and overlapping vibration spectra

Heterostructures like InAs/GaSb superlattices (SLs) are distinctly different from well-studied ones like GaAs/AlAs SLs in terms of band alignment, common interface atom, and phonon spectrum overlapping of the constituents, which manifests as stark differences in their electronic and vibrational properties. This paper reports a comprehensive examination of all four types of phonon modes (confined, quasiconfined, extended, and interface) that have long been predicted for the InAs/GaSb SL, with the observation and interpretation of a set of phonon modes by performing cleaved edge mu -Raman study with polarization analysis. Furthermore, we show a signature of symmetry reduction from D2d for GaAs/AlAs SL to C2v for InAs/GaSb SL revealed as a phonon-polariton effect.