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Résumé:

Dipolar, or indirect excitons (IXs) offer a rich playground for both design of novel optoelectronic devices and fundamental many-body physics. Wide GaN/(AlGa)N quantum wells host a new and promising realization of such excitons. Indeed, compared to their counterparts in GaAs-based heterostructures, IXs in nitrides possess two key advantages. They have higher binding energies, and they are “naturally” indirect. This means, that they can be engineered and manipulated in as-grown heterostructures, even without application of an external electric bias. In this work we demonstrate (i) the propagation of IXs over hundreds of micrometers in the plane of GaN/(AlGa)N quantum wells, (ii) confinement and cooling of these excitons, when trapped in the electrostatic potential created by semitransparent electrodes of various shapes deposited on the sample surface (iii) the electrical control of the IX fluxes via an applied gate voltage. Once confined, the exciton fluid accumulates in uniform zones. By modeling the emission spectra of these zones, we get insight into the thermodynamic properties of the thermalized exciton fluid. These results constitute a prerequisite for realization of the GaN-based excitonic devices, as well for studies of the complex phase diagram of these dipolar bosons at low temperature.