published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaf 110).

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Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

by Won Hon Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 66-70). / by Won Hon Kit. / Acknowledgment --- p.i / Abstract --- p.ii / Chapter Chapter1 --- Introduction --- p.1 / Chapter 1.1 --- Uniqueness of ZnxCd/1-x Se --- p.1 / Chapter 1.2 --- The Choice of OMVPE --- p.1 / Chapter 1.3 --- Epilayer Relaxation in Heteroepitaxy --- p.2 / Chapter 1.4 --- The Most Suitable Substrate --- p.4 / Chapter Chapter2 --- Experimental Procedures --- p.6 / Chapter 2.1 --- Degreasing and Etching --- p.6 / Chapter 2.2 --- Preheating --- p.6 / Chapter 2.3 --- OMVPE Growth --- p.6 / Chapter Chapter3 --- Characterization --- p.9 / Chapter 3.1 --- X-ray Diffraction --- p.9 / Chapter 3.2 --- EDX Spectroscopy --- p.13 / Chapter 3.3 --- Optical Reflectance --- p.15 / Chapter Chapter4 --- Data Analysis --- p.20 / Chapter 4.1 --- Control of Composition --- p.20 / Chapter 4.2 --- Structural Quality and Epilayer Relaxation --- p.22 / Chapter 4.3 --- Critical Point Energies --- p.24 / Chapter 4.4 --- Refractive Index and Extinction coefficient --- p.26 / Chapter Chapter5 --- Conclusions --- p.28 / List of Figures --- p.30 / Reference --- p.66

by Lee Wai Lok. / x and 1-x are in title are subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves [67]-[70]). / by Lee Wai Lok. / Abstract --- p.i / Chapter Chapter1 --- Introduction --- p.1-1 / Chapter 1.1 --- Epitaxial Growth --- p.1-2 / Chapter 1.1.1 --- Background of Epitaxy --- p.1-2 / Chapter 1.1.2 --- Operating Principle of OMVPE --- p.1-2 / Chapter 1.1.3 --- Problems in Heteroepitaxy --- p.1-3 / Chapter 1.2 --- Basic Requirements of a Semiconductor Laser --- p.1-3 / Chapter 1.3 --- Our work --- p.1-4 / Chapter Chapter2 --- OMVPE Growth --- p.2-1 / Chapter 2.1 --- Our OMVPE System Design --- p.2-1 / Chapter 2.1.1 --- Growth Environment --- p.2-2 / Chapter 2.1.2 --- Susceptor Temperature Control --- p.2-2 / Chapter 2.1.3 --- Reactor Pressure Control --- p.2-2 / Chapter 2.1.4 --- MO Vapor Handling Control --- p.2-2 / Chapter 2.1.4.1 --- MO Flow Control --- p.2-3 / Chapter 2.1.4.2 --- Flow Path Selection --- p.2-3 / Chapter 2.1.5 --- Cabinet with Air Extraction --- p.2-3 / Chapter 2.1.6 --- Chemical Scrubber --- p.2-4 / Chapter 2.2 --- System Calibration --- p.2-4 / Chapter 2.3 --- Materials Used --- p.2-5 / Chapter 2.3.1 --- Precursor Materials --- p.2-5 / Chapter 2.3.2 --- Hydrogen Gas --- p.2-5 / Chapter 2.3.3 --- Nitrogen Gas --- p.2-6 / Chapter 2.3.4 --- Substrate --- p.2-6 / Chapter 2.4 --- Fabrication Conditions --- p.2-6 / Chapter Chapter3 --- Characterization --- p.3-1 / Chapter 3.1 --- X-ray Diffraction --- p.3-1 / Chapter 3.2 --- EDX Spectroscopy --- p.3-2 / Chapter 3.3 --- Optical Reflectance --- p.3-4 / Chapter Chapter4 --- Data Analysis --- p.4-1 / Chapter 4.1 --- ZnSe/GaAs(100) --- p.4-1 / Chapter 4.1.1 --- Structural Analysis --- p.4-1 / Chapter 4.1.2 --- Stoichiometry --- p.4-2 / Chapter 4.1.3 --- Growth Rate --- p.4-3 / Chapter 4.1.4 --- Energies of Critical Points --- p.4-3 / Chapter 4.1.5 --- Reflectance --- p.4-4 / Chapter 4.2 --- ZnCdSe/InP(100) --- p.4-5 / Chapter 4.2.1 --- Structural Analysis --- p.4-5 / Chapter 4.2.1.1 --- Structural Quality --- p.4-5 / Chapter 4.2.1.2 --- Crystal Structure --- p.4-5 / Chapter 4.2.1.3 --- Lattice Parameter --- p.4-8 / Chapter 4.2.2 --- Composition Range --- p.4-8 / Chapter 4.2.3 --- Degree of Relaxation --- p.4-9 / Chapter 4.2.4 --- Comparison to Prior Art --- p.4-10 / Chapter 4.2.5 --- Growth Rate --- p.4-11 / Chapter 4.2.6 --- Energies of Critical Points --- p.4-12 / Chapter Chapter5 --- Conclusions --- p.5-1 / Appendix A Calculation of the actual MO Mass Flow --- p.6-1 / Appendix B Interpretation of in-plane Lattice Parameter --- p.6-3 / Appendix C Structure Factor of Wurtzite Lattice --- p.6-4 / References --- p.7-1

In radio astronomy wider observing bandwidths are constantly desired for the reasons of improved sensitivity and velocity coverage. As observing frequencies move steadily higher these needs become even more pressing. In order to process wider bandwidths, components that can perform at higher frequencies are required. The chief limiting component in the area of digital spectrometers and correlators is the digitiser. This is the component that samples and quantises the bandwidth of interest for further digital processing, and must function at a sample rate of at least twice the operating bandwidth. In this work a range of high speed digitiser integrated circuits (IC) are designed using an advanced InP HBT semiconductor process and their performance limits analysed. These digitiser ICs are shown to operate at up to 10 giga-samples/s, significantly faster than existing digitisers, and a complete digitiser system incorporating one of these is designed and tested that operates at up to 4 giga-samples/s, giving 2 GHz bandwidth coverage. The digitisers presented include a novel photonic I/O digitiser which contains an integrated photonic interface and is the first digitiser device reported with integrated photonic connectivity. In the complementary area of analogue correlators the limiting component is the device which performs the multiplication operation inherent in the correlation process. A 15 GHz analogue multiplier suitable for such systems is designed and tested and a full noise analysis of multipliers in analogue correlators presented. A further multiplier design in SiGe HBT technology is also presented which offers benefits in the area of low frequency noise. In the effort to process even wider bandwidths, applications of photonics to digitisers and multipliers are investigated. A new architecture for a wide bandwidth photonic multiplier is presented and its noise properties analysed, and the use of photonics to increase the sample rate of digitisers examined.

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The thesis describes measurements of the velocity-field characteristic of indium phosphide, below threshold by a direct method and above threshold by domain measurements. Comparisons, with good agreement, are made with microwave measurements, below threshold on material from the same slices, and above threshold on material with very similar properties. A historical description of the Gunn effect and domain theory precedes a description of the structure of indium phosphide and a survey of published velocity-field calculations and measurements, showing the difference between 2- and 3-level conduction band models. A value for the T valley deformation potential has previously been deduced from the temperature variation of low-field mobility by adding reciprocal mobilities due to different scattering processes. This method is examined and experimental results of other workers are shown consistent with a lower deformation potential than supposed. Sub-threshold results agree closely with other, published, measurements, using various techniques. Extended to 77 K, the subthreshold method gave results agreeing reasonably with predictions for this temperature, and very well with extrapolations from other calculated and measured data. Published high-field domain measurements made with a pointcontact probe differ greatly from others. Experiments to produce a point-contact probe and associated differentiator with a known performance, and analysis of a simple circuit model indicate that the specimen resistivity controls the probe response, necessitating different probe resistances for different material resistivities. The probe was still found fundamentally difficult to use and is suspected of causing specimen damage due to localised heating under the point. Domain shapes measured agreed with published measurements from capacitive probes, but domain velocity was higher, giving a higher valley velocity (0.76 - 0.99 x 1O ⁷ cm/s). Comparison of the deduced velocity-field curve with published calculations strongly supports a 2-level transfer mechanism.

In radio astronomy wider observing bandwidths are constantly desired for the reasons of improved sensitivity and velocity coverage. As observing frequencies move steadily higher these needs become even more pressing. In order to process wider bandwidths, components that can perform at higher frequencies are required. The chief limiting component in the area of digital spectrometers and correlators is the digitiser. This is the component that samples and quantises the bandwidth of interest for further digital processing, and must function at a sample rate of at least twice the operating bandwidth. In this work a range of high speed digitiser integrated circuits (IC) are designed using an advanced InP HBT semiconductor process and their performance limits analysed. These digitiser ICs are shown to operate at up to 10 giga-samples/s, significantly faster than existing digitisers, and a complete digitiser system incorporating one of these is designed and tested that operates at up to 4 giga-samples/s, giving 2 GHz bandwidth coverage. The digitisers presented include a novel photonic I/O digitiser which contains an integrated photonic interface and is the first digitiser device reported with integrated photonic connectivity. In the complementary area of analogue correlators the limiting component is the device which performs the multiplication operation inherent in the correlation process. A 15 GHz analogue multiplier suitable for such systems is designed and tested and a full noise analysis of multipliers in analogue correlators presented. A further multiplier design in SiGe HBT technology is also presented which offers benefits in the area of low frequency noise. In the effort to process even wider bandwidths, applications of photonics to digitisers and multipliers are investigated. A new architecture for a wide bandwidth photonic multiplier is presented and its noise properties analysed, and the use of photonics to increase the sample rate of digitisers examined.