INTERFACE FORMATION IN INAS/AISB AND INAS/ALAS/ALSB QUANTUM-WELLS GROWN BY MOLECULAR-BEAM EPITAXY

We have used resonant Raman scattering from both longitudinal-optical phonons and interface modes to study the chemical bonding across the InAs/AlSb interface in InAs/AlSb quantum wells grown by molecular-beam epitaxy. The effusion cell shutter sequence at the interfaces was selected for the deposition of either one monolayer of InSb or two to three monolayers of AlAs. In all cases an InSb-like interface mode is observed, indicating the preferential formation of In-Sb interface bonds irrespective of the shutter sequence. The deposition of two or three monolayers of AlAs at the InAs/AlSb interface results in the formation of pseudoternary AlSb1-xAsx barriers rather than binary AlAs interfaces and AlSb barriers, indicating a strong exchange among the group-V atoms. Normal (AlSb on InAs) and inverted (InAs on AlSb) InAs/AlSb interfaces have also been compared, revealing a much stronger InSb-like interface mode for the growth of AlSb on InAs than for the case of InAs grown on AlSb.