Pseudopotential approach to long-period narrow-gap superlattices

The pseudopotential method is used to calculate the electronic structures of long-period narrow-gap InAs-GaSb and HgTe-CdTe superlattices. The variations of the energy gaps with the layer thicknesses and the band offsets, the subband dispersion along the kₓ direction, the charge distributions along the lines connecting atoms in the [011] direction, and the optical-transition matrix elements are obtained. It is found that the crossing of the lowest electronic level and the highest hole level for the superlattice (InAs)ₙ(GaSb)ₙ occurs at the period of 160 A{}. The band offset has an essential effect on the energy gaps of the superlattice (HgTe)ₙ(CdTe)ₙ with longer periods. The behavior of the interface states in the HgTe-CdTe superlattice is also discussed.