Site-controlled InAs single quantum-dot structures on GaAs surfaces patterned by in situ electron-beam lithography

We studied a site-control technique for InAs quantum dots (QDs) on GaAs substrates using a combination of in situ electron-beam (EB) lithography and self-organized molecular-beam epitaxy. In small, shallow holes formed on prepatterned mesa structures by EB writing and Cl2 gas etching, QDs were selectively formed, without any formation on the flat region between the patterned holes. The density of the QDs in each hole was dependent on the hole depth, indicating that atomic steps on the GaAs surfaces act as migration barriers to In adatoms. In an array of holes including 5–6 monolayer steps, a single QD was arranged in each hole.