Electronic band-structure engineering of GaAs/Al_xGa _1-xAs quantum well superlattices with substructures

We report a theoretical investigation on the band structures of electrons in both infinite and finite semiconductor quantum well/barrier superlattices with each unit cell containing alternately two types of materials. When the unit cell of a superlattice, made of GaAs and Al_xGa_1-xAs, is further divided into four and six sublayers of these two materials, narrower passbands and/or broad stopbands can be obtained for electrons with energy slightly larger than the potential barrier. When a finite superlattice has two different periods and each unit cell contains six sublayers of alternating GaAs and Al_xGa_1-xAs, very sharp passbands can be obtained for electron energy right below and above the potential barrier. The results may be used to build a high-Q electron energy filter.