PERIODIC BEHAVIOR OF THE EXCITON OSCILLATOR STRENGTH WITH ALAS THICKNESS IN TYPE II GaAs/AlAs HETEROSTRUCTURES

C. Gourdon, D. Martins, P. Lavallard Groupe de Physique des Solides, Universites Paris 6 et Paris 7 CNRS UMR 75-88, Tour 23, 2 Place Jussieu, 75251 Paris cedex 05, France and E.L. Ivchenko Ioffe Physico-technical Institute, Russian Academy of Sciences 194021 St Petersburg, Russia

Full Text PDF

For a single GaAs/AlAs/GaAs type II pseudodirect double quantum well, as well as for superlattices it was predicted that the oscillator strength of the lowest optical transition has a periodic dependence on the number of AlAs monolayers. The oscillator strength depends on the coupling between the Γ and X electron states. We use samples containing a single GaAs/AlAs/GaAs double quantum well with thickness gradient to show experimental evidence of this effect. The results concerning the Γ-X coupling are obtained from the study of the ratio of photoluminescence intensities of the zero-phonon line and the phonon replica and from their time decay. They show the monolayer dependence of the Γ-X mixing potential. We extend the model describing the Γ-X coupling for ideal interfaces in the frame of the envelope approximation to the case of non-abrupt interfaces and exciton localization. The amplitude of variation of the radiative recombination time due to the Γ-X mixing is well reproduced within this model.

DOI: 10.12693/APhysPolA.100.409 PACS numbers: 78.66.-w, 71.70.-d