Quantum Dots with Perfectly Resonant Emission Energies

Semiconductor quantum dots (QDs) with excellent structural, optical and electronic properties can be easily fabricated by the self-assembled Stranski-Krastanow growth mode. However, in spite of numerous efforts and encouraging results, it has become clear that the bottom-up approach alone can not yield QDs with deterministically controllable electronic properties. Post-growth processing seems at present the only viable path to achieve this goal. Here we employ a focused laser beam both to characterize and to in-situ process single self-assembled QDs by heating them from cryogenic to high temperatures. The heat treatment allows us to blue-shift, in a broad range and with resolution-limited accuracy, the quantized energy levels of charge carriers confined in single QDs. We demonstrate the approach by bringing spatially separated QDs in mutual resonance. This processing method may open the way to a full control of nanostructures at the quantum level.