Electronic states of a superlattice with an enlarged quantum well: A tight-binding approach

We present a theoretical study of the energies and localizations of bound e lectronic states in a finite AlAs/GaAs superlattice (SL) with an enlarged c entered GaAs quantum well (EW). The calculations are performed using a semi -empirical sp(3)s* spin dependent tight-binding model and the surface Green function matching technique. The behavior of the bound states at the Gamma -point of the two-dimensional Brillouin zone is studied for a wide range of EW widths. An interaction between states close in energy is found which le ads to energy shifts and to changes in the localization and/or the orbital character of the interacting states. The conduction band structure is deter mined mainly by the interaction between SL and EW-localized states of equal parity. The valence band reveals a complex structure, dominated by the cou pling between heavy and light hole states and the interaction between the s tates of different real space localization (SL or EW).