Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 61-62). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004. / May, Gary, Committee Chair; Doolittle, William, Committee Member; Brown, April, Committee Member; Wang, Zhong Lin, Committee Member; Ralph, Stephen, Committee Member. Includes bibliography.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 102-106).

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 68-71).

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

For this thesis niobium oxides (NbO [subscript x]) with the goal of obtaining phase pure epitaxial NbO₂ were grown under variable conditions by molecular beam epitaxy (MBE) on different substrates, mostly (111) oriented strontium titanate. The films were characterized by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) and from that their epitaxial relationship to the substrate was determined. With X-ray photoelectron spectroscopy (XPS) the oxidation states and stoichiometry of the films were determined. Asymmetric NbO₂ Nb 3d core-level spectra are clearly seen for the first time in XPS. Additionally, the film thickness was measured by X-ray reflectivity (XRR). Judging from the XPS spectra and diffraction data the goal to grow epitaxial NbO₂ of high phase-purity was achieved. / text

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The quaternary material system In[subscript x]Ga[subscript 1-x]As[subscript y]P[subscript 1-y] is an important material system for optoelectronic devices, specifically covering optimum fiber optic wavelengths. Among the limitations of using this material system concerning photodetector performance is generation of carriers due to material defects and impurities. This dissertation reports on the growth optimization of InGaAs using molecular-beam epitaxy for low-dark-current avalanche photodiodes through the study of the effects of the growth conditions on dark current. An optimum growth temperature of 545°C and arsenic beam equivalent pressure of 2x10⁻⁵ Torr was found for producing the lowest dark current density. Avalanche photodiodes were implemented with a dark current density 80 mA/cm² at 90% of the breakdown voltage.

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