Guided self-assembly of lateral InAs/GaAs quantum-dot molecules for single molecule spectroscopy
1 Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
2 European Synchrotron Radiation Facility, Boîte Postale 220, F-38043, Grenoble Cedex, France
Nanoscale Research Letters 2006, 1:74-78 doi:10.1007/s11671-006-9003-yPublished: 26 July 2006
We report on the growth and characterization of lateral InAs/GaAs (001) quantum-dot molecules (QDMs) suitable for single QDM optical spectroscopy. The QDMs, forming by depositing InAs on GaAs surfaces with self-assembled nanoholes, are aligned along the  direction. The relative number of isolated single quantum dots (QDs) is substantially reduced by performing the growth on GaAs surfaces containing stepped mounds. Surface morphology and X-ray measurements suggest that the strain produced by InGaAs-filled nanoholes superimposed to the strain relaxation at the step edges are responsible for the improved QDM properties. QDMs are Ga-richer compared to single QDs, consistent with strain- enhanced intermixing. The high optical quality of single QDMs is probed by micro-photoluminescence spectroscopy in samples with QDM densities lower than 108 cm−2.