Site-controlled self-organization of InAs quantum dots

In situ site-control techniques for self-organized InAs quantum dots (QDs) have been developed using an electron beam (EB) and a scanning tunneling microscope (STM) probe combined with molecular beam epitaxy. In the in situ EB-assisted process, InAs dots are preferentially formed in shallow, sub-μm-size GaAs holes with the InAs supply. We find that the specific slope of a hole acts as a favorable site for dot formation. In the in situ STM probe-assisted process, the size and pitch of the holes are considerably reduced into nanoscale. InAs QDs are then self-organized only at the hole sites due to strain-induced selective nucleation. Using this process, two- and three-dimensional QD arrays are fabricated with nanometer precision.