Raman spectroscopic study of interfaces in InAs/AlSb and InAs/AlAs/AlSb quantum wells grown by molecular beam epitaxy

Raman scattering from both longitudinal optical phonons and interface modes has been used to study the chemical bonding across the InAs/AlSb interface in GaSb capped InAs/AlSb quantum wells grown by solid-source molecular-beam epitaxy. The effusion cell shutter sequence for the growth of the interfaces was selected for the deposition of either 1 monolayer (ML) of InSb or 2 to 3 MLs of AlAs. The latter growth sequence should in principle strongly favour the formation of AlAs-like interfaces. In all cases an InSb-like interface mode is observed, indicating the preferential formation of In-Sb bonds irrespective of the shutter sequence. This behaviour is in contrast to that found for InAs/GaSb heterostructures where both types of interface bonds, InSb-like and GaAs-like, were observed according to the shutter sequence. The deposition of 2 or 3 MLs of AlAs at the InAs/AlSb interface results in the formation of pseudo-ternary AISb (ind 1-x) As (ind x) barriers rather than binary AlAs interfa ces and AlSb barriers, indicating a strong exchange among the group V atoms.