Miniband structure inInxGa1−xAs-GaAs strained-layer superlattices

Abstract

The miniband structure in strained ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs superlattices is studied using interband transmission and reflectivity in magnetic fields up to 16 T. Measured in-plane effective masses are in good agreement with an eight-band k⋅p envelope-function calculation. Significant coupling through barrier layers 100 Å thick is demonstrated by the presence of a finite miniband dispersion and a reduction in the exciton binding energy for samples with thin well layers. The superlattice Landau levels are observed to saturate in high magnetic fields near the top of the minibands, and this behavior together with the superlattice masses are fitted semiclassically using the envelope-function model. Landau levels from the n=2 exciton are analyzed in an uncoupled sample, and, as this state evolves into an unbound miniband, it is predicted to show very anisotropic quasi-one-dimensional behavior.