Growth and Characterisation of InAs Quantum Dots on GaP/Si Substrates using Droplet Epitaxy by MOVPE

Heterogeneous integration of III-V semiconductor quantum dots with on-axis Si (001) substrates presents an avenue towards the development of quantum technologies on photonic integrated circuits. Leveraging the already mature Si (001) technology in this manner has the potential to significantly reduce costs to manufacturers of such devices. In this thesis, InAs quantum dots have been grown on a thin GaP layer atop Si (001) substrates, using the droplet epitaxy growth method in a metalorganic vapour-phase epitaxy reactor. The first step in this process was the deposition of In droplets; it was found that key characteristics of the droplets such as size and density could be effectively controlled by varying different growth parameters such as deposition time and In flow. Following this, the droplets were crystallised with AsH3 into InAs quantum dots, where it was found that the total amount of In on the surface and the crystallisation temperature were key parameters in determining the resultant dot size and density. Finally, the InAs quantum dots were capped with GaP to investigate optical emission. For this phase of the work, quantum dots on pure GaP substrates were used to eliminate strain considerations associated with growth on Si and to provide a comparison of emission from quantum dots on GaP/Si. It was found that broad photoluminescence emission from the GaP itself was present and it was not possible to definitively ascertain whether the quantum dots were optically active. However, transmission electron microscopy analysis confirmed that quantum dots were indeed epitaxially capped and buried by the GaP matrix, demonstrating droplet epitaxy of InAs quantum dots for the first time on GaP by metalorganic vapour-phase epitaxy.