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We present the molecular beam epitaxy fabrication and optical properties of complex GaAs nanostructures by droplet epitaxy: concentric triple quantum rings. A significant difference was found between the volumes of the original droplets and the final GaAs structures. By means of atomic force microscopy and photoluminescence spectroscopy, we found that a thin GaAs quantum well-like layer is developed all over the substrate during the growth interruption times, caused by the migration of Ga in a low As background.

We present the Molecular Beam Epitaxy fabrication of complex GaAs/AlGaAs nanostructures by Droplet Epitaxy, characterized by the presence of concentric multiple rings. We propose an innovative experimental procedure that allows the fabrication of individual portions of the structure, controlling their diameter by only changing the substrate temperature. The obtained nanocrystals show a significant anisotropy between [110] and [1–10] crystallographic directions, which can be ascribed to different activation energies for the Ga atoms migration processes.

A systematic optical study, including micro, ensemble and time resolved photoluminescence of GaAs/AlGaAs triple concentric quantum rings, self-assembled via droplet epitaxy, is presented. Clear emission from localized states belonging to the ring structures is reported. The triple rings show a fast decay dynamics, around 40 ps, which is expected to be useful for ultrafast optical switching applications.

Erratum to: Nanoscale Res. Lett.DOI 10.1007/s11671-010-9689-8The authors’ affiliations have been published incorrectly.Correct authors’ affiliations:S.Bietti,C.Somaschini,E.Sarti ,N.Koguchi,S.Sanguinetti(*)L-NESS and Dipartimento di Scienza dei Materiali,Universita’ di Milano Bicocca, Via Cozzi 53, 20125Milano, Italye-mail: stefano.sanguinetti@mater.unimib.itG. Isella, D. Chrastina, A. FedorovCNISM, L-NESS and Dipartimento di Fisica delPolitecnico di Milano, Via Anzani 42, 22100 Como, Italy

C. Somaschini, S. Bietti, N. Koguchi, S. Sanguinetti (*) L-NESS and Dipartimento di Scienza dei Materiali, Universita’ di Milano Bicocca, Via Cozzi 53, 20125 Milano, Italy e-mail: stefano.sanguinetti@mater.unimib.it A. Fedorov CNISM, L-NESS and Dipartimento di Fisica del Politecnico di Milano, Via Anzani 42, 22100 Como, Italy Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

We present of a detailed photoluminescence characterization of high efficiency GaAs/AlGaAs quantum nanostructures grown on silicon substrates. The whole process of formation of the GaAs/AlGaAs active layer was realized via droplet epitaxy and migration enhanced epitaxy maintaining the growth temperature a parts per thousand currency sign350A degrees C, thus resulting in a low thermal budget procedure compatible with back-end integration of the fabricated materials on integrated circuits.

We propose a self-assembling procedure for the fabrication of GaAs islands by Droplet Epitaxy on silicon substrate. Controlling substrate temperature and amount of supplied gallium is possible to tune the base size of the islands from 70 up to 250 nm and the density from 107 to 109 cm−2. The islands show a standard deviation of base size distribution below 10% and their shape evolves changing the aspect ratio from 0.3 to 0.5 as size increases. Due to their characteristics, these islands are suitable to be used as local artificial substrates for the integration of III–V quantum nanostructures directly on silicon substrate.

We have shown that it is possible to tune, up to complete suppression, the photoluminescence superlinear dependence on the excitation density in quantum dot samples at high temperatures by annealing treatments. The effect has been attributed to the reduction of the defectivity of the material induced by annealing.