Regimes of GaAs quantum dot self-assembly by droplet epitaxy

Two regimes are observed for the density of strain-free GaAs quantum dots (QDs) grown by Ga droplet epitaxy. QDs grown from liquid Ga droplets deposited at temperatures up to $200\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ exhibit densities that qualitatively agree with classical nucleation theory and are quantitatively reproduced by a rate equations based growth model under consideration of dimer break off. In contrast, at higher growth temperatures, the onset of coarsening by Ostwald ripening [Z. Phys. Chem., Stoechiom. Verwandtschaftsl. 34, 495 (1900)] causes drastically reduced QD densities. Extension of the growth models and consideration of Ostwald ripening allow the quantitative prediction of QD densities in this regime, as well.