Semiconductor quantum dots (QDs), with quasi zero-dimensional confinement of carriers present interesting electronic and optical properties. Quantum dot materials have found potential applications as lasers, photon detectors, photon amplifiers, quantum cryptography, quantum computation, etc. The possible realization of single photon quantum emitters and photon (or carriers) entanglement is nowadays a central point in QDs investigation. Crucial issues in the progress of QDs exploitation as non classical photon sources is the knowledge and the control of the local environment and of the intrinsic structural properties.
We experimentally investigate the optical and electronic (excitonic) properties of self assembled, strain-free, GaAs/AlGaAs nanostructures grown by modified droplet epitaxy (MDE) with particular attention to the QD and concentric quantum ring (CQR) cases. The experimental technique is photoluminescence (PL) spectroscopy on single nano-emitters excited by continuous and pulsed laser beams. The main topics of the presentation are : i) the spectral diffusion of different excitonic complexes ; ii) the anisotropic exchange interaction between charge-spins ; iii) the demonstration of single photon emission from MDE concentric quantum rings.