Design, fabrication and spectroscopy of strain-turnable quantum dots in nanowire antennas

Single-photon sources with high brightness, resolution-limited linewidths, and wavelength tunability are promising for future quantum technologies. This thesis investigates elastically tunable quantum dots(QDs) inside nanowire antennas which are fabricated and studied using photoluminescence spectroscopy and time correlated single photon counting at cryogenic temperature. For the nanofabrication, a new electron beam lithography system and a reactive ion etch chamber have been calibrated and maintained. GaAs nanowires with diameters as low as 120 nm and aspect ratios as high at 1:18 were successfully fabricated. These nanowires were structurally characterized by single electron microscopy. A sample with nanowires containing QDs was vertically bonded to a piezoelectric crystal. To carry out experiments at low temperature, two commercial and one home-built pulsed-tube cryostats were assembled. A miniature confocal microscope, which can be used inside the home built cryostat, was assembled and characterised. A confocal microscope to carryout spectroscopy at telecom wavelength,to be used with the commercial cryostats, was assembled and used in experiments by other group members. A third microscope for near infrared spectroscopy was assembled, to carry out spectroscopic characterization of the strain tunable device. And reveals that the nanowire geometry influences the extraction efficiency (η). For the brightest nanowire, we estimated η ≈57 %. We find that non-resonant excitation leads to static (fluctuating) charges, likely at the nanowire surface, causing DC Stark shifts (inhomogeneous broadening); for low excitation powers, the effects are not observed, and resolution-limited linewidths are obtained. Despite significant strain-field relaxation in the high-aspect-ratio nanowires, we achieve up to 1.2 meV tuning of a dot’s transition energy