Influence of ultra-thin AlAs barriers on the optical properties of GaAs/AlGaAs quantum-well structures

摘要

The optical properties of AlGaAs/AlAs/GaAs double barrier quantum well (DBQW) structures, obtained by the insertion of ultra-thin barriers of AlAs between the Al$-x$/Ga$-1$MIN@x$/As alloy and the GaAs wells, are investigated by means of continuous-wave and time-resolved photoluminescence techniques. Particular attention is devoted to the structure of the electronic states and to the recombination lifetime of the photoexcited carriers. We demonstrate the usefulness of this novel type of heterostructure as a further degree of freedom toward a tailoring of the band edges in GaAs/AlGaAs QW systems and also for the study of the carrier dynamics in the limit of very shallow subbands. Clear evidence of the transitions between 2D - 3D exciton behavior and between type I - type II recombinations are found depending on the thickness of GaAs and AlAs layers.