Controlled type-I-type-II transition in GaAs/AlAs/AlxGa1-xAs double-barrier quantum wells

We show that the insertion of extremely narrow AlAs layers in double-barrier GaAs/AlAs/AlxGa1-xAs quantum wells results in a variety of electronic configurations, thus providing a powerful tool for tailoring the electronic transitions in GaAs heterostructures. In particular, the transition from type-I to type-II recombination is shown to occur in correspondence with variations by a single monolayer in the thickness of the AlAs and/or GaAs layers. Drastic changes in the recombination lifetimes are correspondingly observed; at the same time, the photoluminescence efficiency is found to be almost independent of the type-I-type-Il character of the transition.