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Title: Quantum dot single photon sources fabricated using novel processing techniques
Author: Ellis, David Julian Peter
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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This thesis details the development of a range of single photon source architectures, based on self-assembled InAs QDs. Unlike similar devices reported elsewhere [13, 67, 128, 187], the semiconductor heterostructures employed here are modified from their as-grown condition using a wet oxidation technique to convert aluminium-rich A1xGa1-x;As layers into aluminium oxide [38]. Oxidation can proceed laterally into a semiconductor heterostructure through exposed sidewalls, allowing the formation of regions of oxide within a device [33]. These layers exhibit a refractive index of around 1.5 and are excellent electrical insulators. In this work, oxide layers are employed in a number of different situations. In an electrically driven device, a ring of oxide was used to form a current aperture. This allowed an individual quantum dot to be electrically addressed. Oxide layers were employed to form high contrast mirrors in semiconductor pillar microcavities, from which enhanced spontaneous emission was observed. Oxide apertures were also integrated into Ga/As/A1xGa1-x;As microcavity structures, where the aperture can result in both optical and electrical confinement. Finally, rapid thermal annealing was investigated and demonstrated to be a useful tool to tune the emission energy and fine structure splitting of individual InAs quantum dots. A series of short anneals was shown to blueshift the exciton emission line of any selected quantum dot, accompanied by a reduction and inversion in polarisation splitting.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral