Development and Characterisation of Site-Controlled Quantum Dot Waveguides for Nanophotonics Devices

The objective of this study is to investigate the growth and optical properties of positioned InAs quantum dots (QDs) on GaAs (001) substrates, grown by molecular beam epitaxy for nanophotonic applications. The research presents the impact of growth techniques, such as growth interrupt and indium flushing on site-controlled structures, and demonstrates the ability to reduce the size distribution of QDs within a patterned array and control QD emissions with the use of such growth techniques. Low-temperature micro-photoluminescence was used to characterise positioned InAs QDs, including QD occupancy and single dot emissions, excitonic states and fine structure splitting. Site-selected arrays was also presented as a QD map, showing groups of neighbouring QDs with comparable optical properties which could be tuned using stark effect in a doped structure. Following from the successful undoped structures, the growth of doped site-controlled waveguides was presented and successfully fabricated into mesa diodes. With a diode structure, an electric field was applied providing the ability to tune multiple QDs into the same wavelength. In addition, the use of post-growth method to control QD emissions was presented. The use of rapid thermal annealing with different capping methods on InAs/InP QDs was demonstrated and the ability to control emissions wavelength using annealing temperature between 750°C and 800°C with a SiO¬2 cap was demonstrated. The QD properties such as integrated PL intensity, wavelength shifting, and FWHM have also been shown to improve after RTA. Low-temperature micro-photoluminescence of the annealed structures showed similar improvements to single QD emissions where wavelength shifting of single dots and reduction to QD linewidths is achieved.