Electronic properties of AlGaAs-based biperiodic superlattices via pseudopotential calculations

Abstract

According to recent model studies, AlGaAs-based biperiodic superlattices (SLs), in which every second GaAs slab (`quantum-well' layer) and/or every second AlAs slab (`quantum-barrier' layer) is of a different width, exhibit superior characteristics as compared to usual SLs with simple two-layer well/barrier period. Consequently, they are found promising for novel applications in optoelectronics. However, the transferability of conclusions based on results of simplified approaches to real systems is often questionable. Therefore, we have carried out more reliable pseudopotential computations of the electronic level structure and space-charge distributions for [100]-oriented biperiodic (GaAs)k(AlAs)l(GaAs)m(AlAs)n SLs with variable layer thicknesses. More specifically, we have employed a standard supercell calculation scheme with a plane wave basis set and implemented modern empirical 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 Γ-valley-derived minibands reproduce the characteristics predicted by simple-model approaches, the corresponding features of the AlAs X-valley-derived minibands, which are neglected in most model studies although being of a particular importance for thin-layer systems, are discussed for biperiodic SLs for the first time.