WANNIER-STARK LOCALIZATION IN MODULATION-DOPED MULTIPLE-QUANTUM-WELL STRUCTURES

The external-electric-field effect and the doping effect on a modulation-doped finite-length GaAs/AlxGa1-xAs superlattice have been studied by solving the Schrodinger-Kohn-Sham equation and the Poisson equation self-consistently. In the heavy-doping case, the external electric field makes electrons sequentially tunnel through several potential barriers, and accumulates electrons near one side of the finite-length superlattice. The collective motion of the electrons results in high- and low-field domains in the superlattice. We have found that Wannier-Stark localization exists only in the high-field domain, and that the electronic states are not evenly spaced. The electric-field-induced (doping induced) depopulation (population) of subbands has been studied. We have also found oscillatory behavior of the calculated conductivity near the Fermi energy as a function of the external electric field.