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Site-controlled single-photon emitters fabricated by near-field illumination

We developed, in collaboration with the group at Physics departments of Sapienza University of Rome (Dr. M. Felici) and of University of Florence (Dr. F. Biccari), a novel and versatile approach for the fabrication of site-controlled, single-photon emitting quantum dots. Hydrogen incorporation in GaAsN semiconductors results in the formation of N–H complexes, which neutralize all the effects of N on GaAs, including the N-induced large reduction of the bandgap energy. Starting from a fully hydrogenated GaAsN/GaAs quantum well, the N–H bonds located within the light spot generated by a scanning near-field optical microscope tip are broken, thus obtaining site-controlled GaAsN quatum dots (QDs) surrounded by a barrier of GaAsN:H (laterally) and GaAs (above and below). By adjusting the laser power density and exposure time, the optical properties of the QDs can be finely controlled and optimized, tuning the quantum confinement energy over more than 100 meV and resulting in the observation of single-photon emission from the QD. This novel fabrication technique features state-of-the-art control over both the nanostructure position (< 100 nm) and emission energy (≈ 20 meV) and it can easily be applied to the realization of more complex nanostructures.


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