STRAIN COMPENSATION IN LATTICE-MISMATCHED SHORT-PERIOD SUPERLATTICES

The electronic properties of [001] (AlAs)(n)-(AlSb)(n) short-period st rained-layer-superlattices (SPSLS) lattice matched to InP, for n less than or equal to 4, have been calculated with a first-principles self- consistent pseudopotential method. The layer dependence of the interpl anar relaxations, direct and indirect band gaps, and spin-orbit and va lence band strain splittings are studied. Evolution of the superlattic e states from the bulk constituents is discussed in terms of wavefunct ion mixing and band repulsion due to zone-folding. The band structures of the SPSLSs are compared with a disordered alloy of AlAs0.5Sb0.5 re presented by the special quasirandom structure. We fmd that continuum models of the total valence band splitting (strain and spin-orbit) do not accurately represent the electronic structure of lattice mismatche d SPSLS, due to strong mixing of the heavy-and light-hole states acros s the interface. (C) 1998 Academic Press Limited.