Interband and intersubband transitions in photoexcited mixed type I and type II GaAs/AlAs superlattices

We present a study of the interband and intersubband transitions in mixed type I and type II GaAs/AlAs superlattices. Depending on the energy and intensity of the exciting (laser) radiation, either excitons in the wide GaAs wells or separate 2DEG and 2DHG are formed in the wide and narrow GaAs wells, respectively. We observe both the direct interband transitions and the inter-well transitions, and identify them by comparison with the calculated conduction and valence subband dispersion relations and resulting spectra. Intersubband transitions of the photoexcited 2DEG are observed as well. Under the application of an external magnetic field, the interband transitions between electron and hole Landau levels are shown to be strongly dependent on the density of the photoexcited 2DEG.