Confinement in the GaSb-InAs(001) superlattice

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Abstract
The authors have used non-local pseudopotentials with spin-orbit coupling to study the processes of confinement in a GaSb-InAs(001) superlattice of period 36 AA as a function of the difference between the average bulk crystal potentials. They show that short-wavelength scattering is the prime mover in the physical processes leading to the confinement of charge. Although long-wavelength scattering processes act largely as a delocalisation mechanism which tends to increase the interaction between different states, their presence is essential in the formation of a stable electronic system. In addition, they have shown the form of the confined states that exist in the absence of a band offset and have indicated the effects of band mixing on confinement. They have shown that although a superlattice state may not show confinement in the conventional sense (i.e. in the sense of the envelope function approximation), confinement may take place in particular networks of bonds. They have probed the different optical properties that may be exhibited by the various superlattice states with varying band offsets and have highlighted the link between these optical properties and the form of the confined states. In particular, they indicate the different optical properties associated with resonant states in type I and type II superlattices. They also show that even for GaSb-InAs systems comprising ultra-thin layers, the envelope function model Hamiltonian remains a useful practical tool for states lying closest to the band edges.