Electronic properties of AlGaAs-based biperiodic superlattices via pseudopotential calculations

According to recent model studies, AlGaAs-based biperiodic superlattices (S Ls), in which every second GaAs slab ('quantum-well' layer) and/or every se cond AlAs slab ('quantum-barrier' layer) is of a different width, exhibit s uperior characteristics as compared to usual SLs with simple two-layer well /barrier period. Consequently, they are found promising for novel applicati ons in optoelectronics. However, the transferability of conclusions based o n results of simplified approaches to real systems is often questionable. T herefore, we have carried out more reliable pseudopotential computations of the electronic level structure and space-charge distributions for [100]-or iented biperiodic (GaAs)(k) (AlAs)(t) (GaAs)(m) (AlAs)(n) SLs with variable layer thicknesses. More specifically, we have employed a standard supercel l calculation scheme with a plane wave basis set and implemented modern emp irical pseudopotentials. The SL potential resulting from the two different GaAs and/or AlAs slabs within the SL period yields miniband splittings and specific spatial redistributions of states. While our results obtained for the GaAs Gamma -valley-derived minibands reproduce the characteristics pred icted by simple-model approaches, the corresponding features of the AlAs X- valley-derived minibands. which are neglected in most model studies althoug h being of a particular importance for thin-layer systems, are discussed fo r biperiodic SLs for the first time. (C) 2001 Elsevier Science B.V. All rig hts reserved.