Morphology and wetting layer properties of InAs/GaAs nanostructures

In this work, we present the growth of InAs rings by droplet epitaxy. A complete process from the rings formation to their density saturation has been demonstrated. A morphological evolution with the varying of the indium deposition amount has been clearly observed. Our results indicate that there is a critical deposition amount (∝1.1 ML) for the indium to form InAs dots before droplets form; there is also a critical deposition amount (∝1.4 ML) to form InAs rings, but it is caused by the formation of droplets as the deposition amount increases. The density of the rings saturates when the deposition amount exceeds ∝3.3 ML, because the adsorbed indium atoms block sites for further adsorption and the following supplied In only contributes to the size increase of In droplets. Still, as the In deposition amount increases, we can find coupled quantum rings. Moreover, the wetting layer properties of these structures are studied by reflectance difference spectroscopy, which shows a complicated evolution with the In amount. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)