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 sub strates using a combination of in situ electron-beam (EB) lithography and s elf-organized molecular-beam epitaxy. In small, shallow holes formed on pre patterned mesa structures by EB writing and Cl-2 gas etching, QDs were sele ctively formed, without any formation on the flat region between the patter ned holes. The density of the QDs in each hole was dependent on the hole de pth, indicating that atomic steps on the GaAs surfaces act as migration bar riers to In adatoms. In an array of holes including 5-6 monolayer steps, a single QD was arranged in each hole. (C) 2000 American Institute of Physics . [S0003-6951(00)01602-8].