ORA Thesis: "Optical spectroscopy of wide bandgap semiconductor nanoscale structures" - uuid:b8318654-dd3a-4875-8a8e-1e57d877b0f2




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Reference: Mark J. Holmes, (2011). Optical spectroscopy of wide bandgap semiconductor nanoscale structures. DPhil. University of Oxford.

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Title: Optical spectroscopy of wide bandgap semiconductor nanoscale structures


The optical properties of GaN nanocolumn structures containing InGaN quantum disks are investigated by optical microphotoluminescence spectroscopy using pulsed lasers, and cathodo- luminescence. The results are analyzed in the context of current theories regarding an inho- mogeneous strain distribution in the disk which has been theorized to generate lateral charge separation in the disks by strain induced band bending, an inhomogeneous polarization field distribution, and Fermi surface pinning. Simulations of the strain distribution for the relevant materials and structures are also performed, and the results analysed. It is concluded from ex- perimental measurements that no extreme lateral separation of carriers occurs in the quantum disks under investigation. Internal field screening by an increased carrier density in the QDisks at higher excitation densities is observed via a blue-shift of the emission and a dynamically changing decay time. Other possible explanations for these effects are discussed and discounted.

Microphotoluminescence studies are also carried out on a single GaN nanocolumn struc- ture that has been removed from its growth substrate and dispersed onto a patterned grid. An analysis of the dynamics of the carriers in the nanocolumn is presented. Suppression of the GaN luminescence from the area of the column in the vicinity of the InGaN QDisk in addition to a delayed emission from the QDisk relative to the GaN is observed. Time resolved spatial maps of the luminescence intensity from the column are also presented, illustrating the evolution of the carrier density in the system.

Additional, albeit early-stage, work on novel structures based on the production of GaN nanocolumns, namely nanotubes and nanopyramids, is also presented.

Digital Origin:Born digital
Type of Award:DPhil
Level of Award:Doctoral
Awarding Institution: University of Oxford
About The Authors
institutionUniversity of Oxford
facultyMathematical,Physical & Life Sciences Division
Prof R. A. Taylor More by this contributor
Bibliographic Details
Issue Date: 2011
Copyright Date: 2011
Urn: uuid:b8318654-dd3a-4875-8a8e-1e57d877b0f2
Item Description
Type: thesis;
Language: en
Member of collection : ora:thesis
Alternate metadata formats
Copyright Holder: Mark Holmes
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