Site-selective growth of self-assembled InAs quantum dots on focused ion beam patterned GaAs

A site-selective growth of self-organized InAs quantum dots (QDs) employing a combination of in-situ focused ion beam (FIB) implantation and self-organized molecular beam epitaxy (MBE) growth has been successfully demonstrated. First, a buffer layer of GaAs was grown by MBE before a square lattice of shallow holes with a pitch of 1–2 μm was fabricated by FIB implantation of Ga and In ions. Before InAs deposition, different procedures to remove the implantation damage were tested. The best results were obtained after re-evaporation of 3–5 nm GaAs. Another critical parameter that was carefully optimized is the deposited InAs amount. For the optimized process it was possible to induce growth of single QD in the hole with more than 50% probability. Between the shallow holes of 2 nm depths, no QD growth was observed. The optical quality of positioned dots was investigated by photoluminescence spectroscopy, employing a separate sample where the QDs were overgrown by GaAs cap layer. Excited-state interband transitions up to n=5 were observed from positioned QDs.