| The research work in this doctoral thesis was mainly supported by the subproject one "Theory on heterogeneous materials compatibility and Key structure&Technology Innovations for Monolithic Integrated Optoelectronic Devices" (No.2003CB314901), which belongs to the "Basic Research on Integrated Optoelectronic Devices and Microstructure Optical Fibers with Structure and Technology Innovations for Future Advanced Optical Communications", National Basic Research Program of China(Project No.2003CB314900), which Professor Ren Xiaomin is responsible for as a chief scientist. Additionally, a part of the research work was also assisted by the project "Material Technology Research on GaAs and InP-based Functional Tapered Structure and Applications in Novel Optoelectronic Devices", the National Natural Science Foundation of China (No.90201035). The work was mainly focused on the compatibility issues of large mismatched integrations of heterogeneous materials. Research results, as listed below, have been achieved.1. The surface morphologies of low temperature InP buffer layer grown on GaAs (001) substrate by metalorganic vapor deposition were examined in detail. By properly selecting growth temperature, three kinds of nanostructure, i.e. islands, pits and ripples were formed. For growth temperature of 400-450℃, the surface morphologies were governed by islands; but, for the growth temperature of 500°C, the surface ripples took place. On the other hand, the observation of enhanced growth of pits upon a high temperature annealing (at 685°C for 90s) indicated that the strained InP epitaxial film would be morphologically stabilized by taking the form of pits formation. We also show that the strained-induced surface roughening is thermally activated when the misfit strain exceeded a certain valueεc and the temperature-controlled InP nanostructures will take form. This aim was to determine the correlation between the surface morphology and the growth conditions during InP/GaAs heteroepitaxy, which would provide an avenue to spontaneous and stable nanostructures.2. The mechanical behaviour of low temperature (LT) buffer layers for InP/GaAs heteroepitaxy using MOCVD has been investigated by x-ray diffraction (XRD). It has been found that LT-InP/LT-GaAs double LT buffers were more effective for strain accommodation than LT-InP single buffer during InP/GaAs epitaxy. It was demonstrated the double buffers were deformend along growth direction at the initial growth stage by XRD profiles, thus aiding in the accommodation of the strain induced by lattice mismatch. This work contributes direct evidence in support of the proposal that thin buffer layers in layer-by-layer semiconductor heteroepitaxy exhibit mechanical behavior similar to that of compliant substrates.3. The Epitaxial lateral overgrowth (ELOG) of InP on InP/GaAs substrates by MOCVDwas investigated. The surface characterization of overgrowth InP was dependent on theⅤ/Ⅲratio, the mask width and the growth time. When the mask width is less than 5μm and theⅤ/Ⅲvalue is below 300, the sidewalls of ELO InP become roughening with the multiple crystal facets, i.e. facet competing effect. However, increasing the mask width in the range of 5 to 20μm will smooth the sidewalls. Furthermore, theoretical expressions of the ELOG rate in MOCVD have been formulated, with respect to two separate processes: vapor phase diffusion and mask surface diffusion. On the condition of InP deposition on GaAs substrate, a parametric study was accomplished in order to determine the impact of the mask/window width to the growth rate. The model, which was calculated by Finite Element Method, revealed that the key determining factors of the growth rate are mask/window width and mask width/effective mask length.4. We have investigated the electronic structure of new semiconductor alloys BxGa1-xAs and TlxGa1-xAs, employing first-principles calculations within the density-functional theory and the generalized gradient approximation. The disordered zinc-blende alloys are modelled using cluster expansion approximation, which allows for taking into account local structural relaxation. The calculations show that a band-gap bowing behavior for BxGa1-xAs is stronger than that of TlxGa1-xAs, which stems from the different impact of atomic relaxation on the electronic structure. Furthermore, it is difficult to obtain as high as 14% Tl conceration in TlxGa1-xAs due to the large atomic size difference between Tl and Ga. This work has been provided further evidence for the experimental investigation of new characteristic of B-related alloys.5. Single crystal zinc-blende BxGa1-xAs epilayers have been successfully grown on (001) GaAs substrates by low pressure metalorganinc chemical vapor deposition. Triethylboron, trimethylgallium and arsine were used as precursors. The maxium boron composition up to 5.8% is obtained at the growth temperature of 580℃, and test results obtained by atomic force microscopy and XRD demonstrated good quality of BxGa1-xAs epilayers.
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