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Structures containing multiple layers of self-assembled InAs quantum dot clusters within a GaAs matrix are investigated on GaAs (1 0 0) by atomic force microscopy. Droplet homoepitaxy (GaAs nanostructures on planar GaAs) is used to create tiny GaAs nano-mound templates elongated along [0 1 −1]. Due to a high density of monolayer steps on the edge of nano-mounds, deposited InAs prefer to form in clusters around the nano-mound templates. By varying the subsequent InAs monolayer coverages and growth temperatures, two distinctive sizes of quantum dots (QDs) are formed around the nano-mounds for the layer stacking. With a fixed GaAs barrier thickness (10 nm) in between the layers, the resulting QDs from the stacked layers show significant improvement in their size uniformity.

New morphologies of InAs quantum dot (QD) ensembles forming on self-assembled GaAs nano-holed island templates are demonstrated. Droplet homoepitaxy (GaAs/GaAs) is used to generate holed nanoscale-sized mounds that appear to elongate along . Depending on the InAs monolayer (ML) coverages, subsequent InAs deposition forms different sizes and shapes of QD ensembles. While we initially observe the formation of the QDs at the hole sites when less InAs is deposited, QDs form around the edges of the mounds with greater InAs deposition. By varying the InAs depositions and growth temperatures, we demonstrate an ability to control the size and density of QDs. The observed decrease in the necessary critical thickness required for the InAs 2D–3D transition may be due to the higher density of monolayer steps on the sidewalls of the holes and on the edges of the mounds. This hybrid growth approach overcomes some limitations of typical QD growth on planar GaAs surfaces and may find applications in optoelectronics.

State University of New York, Buffalo, New York, USA U.S. Army Research Laboratory, Adelphi, Maryland 20783, USA SUNY Polytechnic Institute, Albany, New York, USA Memory R&D Division, SK Hynix, Icheon-si, Gyeonggi-do, 467-701, Korea Center for Micro- and Nanostructures, TU Vienna, Vienna 1040, Austria