Electric and magnetic field induced dimensionality reduction in InGaAs-GaAs superlattices

Abstract

We have measured photoconductivity spectra in a InGaAs/GaAs superlattice subjected to longitudinal electric and magnetic fields. We have observed a clear sharpening of the excitonic features in the spectra as the fields increases. Furthermore, the intensity of excitons involving spatially separated electrons and holes increases with increasing magnetic field relative to that of vertical excitons. These observations can be interpreted with a model that lakes into account exciton wavefunction shrinkage induced by magnetic field. Oblique excitons have a smaller binding energy than vertical excitons and are therefore more sensitive to magnetic localization, which enhances their oscillator strength relative to that of vertical excitons. Strong exciton interactions are also observed, giving rise to level anticrossings.