Résumé
This lecture will present the specific features of GaN- and ZnO-based quantum wells that make them interesting candidates for the creation and manipulation of dipolar, indirect excitons. Conceived as a comparison with what is currently obtained in biased GaAs-based structures, the presentation will emphasize the consequences of a number of properties such as: (i) much larger exciton binding, (ii) much larger Mott densities, (iii) built-in electric fields larger by one order of magnitude, (iv) the subsequent radiative lifetimes that can easily reach several tens of µs… Actual material properties that can be considered detrimental, at present, will also be discussed, like the current crystalline quality of the materials, inducing high densities of nonradiative defects.Theoretical and experimental results will be commented, in order to illustrate the current understanding of the physics of the dipolar excitons that appear naturally in these systems, with no need of an externally applied electric field. In particular, the change of exciton energies under high-density conditions will be discussed. The complex recombination dynamics, measured by time-resolved spectroscopy, will be explained. Recent results on the in-plane propagation of those dipolar excitons will be shown.