Superlattice dispersion in InGaAs/InGaAsP multi-quantum wells

Interband magneto-optical absorption has been studied on InGaAs/InGaAsP superlattice structures. In addition to the well known E1-HH1, E1-LH1, E2-HH2 confined state transitions, the observation of the strong transitions from the valence band continuum to the E1 and E2 states allows one to make reliable estimates of the band discontinuities in this system, giving Delta Ec=0.377 Delta Eg. Application of a magnetic field both perpendicular and parallel to the superlattice layer planes allows one to deduce the superlattice dispersion, showing a large reduction in the electron mass along the superlattice direction for the E2 band due to the formation of zone-folded minibands. The electron mass of the motion in the layer planes for the same band also shows a reduction over the equivalent bulk alloy.