Spectroscopic evidence of the dissymmetry of direct and inverted interfaces in GaAs/AlAs type-II superlattices

In type-II pseudodirect superlattices (SL's) the study of the polarization of photoluminescence in a magnetic field along the growth axis brings insight into exciton localization and interface quality. We demonstrate that excitons in a given sample are not localized at random at the direct or inverted interface, but mostly at one type of interface. For each sample we determine the nature of this interface. This determination is made possible by the study of two asymmetrical superlattices in which excitonic recombination is forced at one type of interface by the design of the band structure. In nominally symmetrical SL's, i.e., with a two-layer period, we show that localization at the direct or the inverted interface is determined by the growth conditions, namely, the substrate temperature and growth interruption at interfaces. [S0163-1829(98)03607-8].