Samples of epitaxial structures with GaAs/AlGaAs quantum rings different in morphology are grown by droplet epitaxy. The photoluminescence spectra of the samples are recorded at temperatures of 20–90 and 300 K. Intense peaks defined by quantum confinement of the charge-carrier energy in the quantum rings are observed in the optical region. The peaks are identified by estimating the energy of the ground state of electrons and holes in GaAs quantum rings and by recording the spectra of the samples after removing the layers with the quantum rings by etching. The average dimensions of the quantum rings are determined by atomic force microscopy and scanning electron microscopy. Some inferences about the factors that influence the emission spectrum and intensity of the epitaxial structures with quantum rings are drawn.

The effect of the hybridization of quantum states on electron transport in a two-barrier quantum well δ-doped through a spacer layer at the limit of heavy doping is shown theoretically and experimentally. A method for increasing the electron mobility in the quantum well by suppressing the tunnel coupling with the donor region through the introduction of an AlAs nanobarrier into the spacer layer is proposed. It is experimentally shown that, in the samples with a shallow quantum well, the AlAs nanobarrier introduced into the spacer layer provides a larger than threefold increase in the electron mobility at low temperatures.

Samples with arrays of GaAs/AlGaAs quantum rings (QRs) of different shapes were grown by molecular beam epitaxy in droplet epitaxy mode. Photoluminescence (PL) spectra of the samples were measured at 20 — 90 K and 300 K, intense peaks attributed to the QR layers were observed. The peaks were identified by comparison of as-grown and selectively etched samples and by the calculation of the ground state energy for charge carriers in GaAs QRs. FWHM narrowing with the temperature increase was observed below 70 K.

The drop epitaxy process in the GaAs/AlGaAs system is experimentally and theoretically studied. Epitaxial structure samples with arrays of single and double quantum rings are grown under various growth conditions. Diffusion processes of Ga and As adatoms are considered, steady-state diffusion equations are analytically solved, and the formation mechanisms of single and double quantum rings are revealed. The results obtained make it possible to model the quantum ring profile depending on growth conditions and, hence, to control the nanostructure profile during drop epitaxy.