Strain-induced electron states in Si0.75Ge0.25(Si/Si0.5Ge0.5)(001) superlattices

The authors have carried out a pseudopotential calculation of the electronic structure of a strained Si/Si0.5Ge0.5 superlattice in which the effect of strain peculiar to the choice of substrate (i.e. Si0.75Ge0.25) and that of the microscopic potential of the individual layers are fully accounted for. They report several strain-induced well confined electron states localised in the silicon layers. They find that the optical matrix element for the transition across the fundamental superlattice gap is quite small.