| Defects in III-V compound semiconductors controlled by crystal growth and materials processing can strongly influence material properties critical to electronic performance. In this thesis, partial dislocation core structures, inversion domains and precipitates are major defects that have been studied in three different III-V compounds.; Although a great number of studies have been aimed at understanding the core structures of dislocation in semiconductors, much is still unknown. In the thesis, the structure of an isolated, Ga terminated, 30° partial dislocation in GaAs: Be is determined by HRTEM and a focal series reconstruction method. A quantitative comparison of the structure predicted by an ab initio electronic structure total energy calculation for the experiment indicates that theory and experiment agree to within 20 pm. Further analysis shows that the deviations between theory and experiment appear to be systematic. Electron energy loss spectroscopy (EELS) establishes that defects segregate to the core region, thus very possibly accounting for the systematic deviations.; The microstructural characteristics of single crystal GaN thin film which was deposited epitaxially on a HfN-buffered Si(111) substrates by molecular-beam epitaxy were studied. Cross-sectional TEM investigations have revealed the crystallographic orientation relationship in different GaN/HfN/Si layers. GaN film polarity is studied by conventional TEM and simulations, and the results show that the GaN film has a Ga polarity with relatively high density of inversion domains. Based on our observations, growth mechanisms related to those structural properties are discussed.; Precipitates are one common defect in InN thin films, which have been grown epitaxially on GaN-buffered sapphire substrates by molecular-beam epitaxy at 500°C. A high level of oxygen contamination in the growth chamber led to the formation of In2O3 precipitates in the films. The concentration of In2O3 was estimated to be less than 0.07 vol.% in the present samples of oxygen content ∼0.5 at.%. Cross-sectional TEM investigations revealed that the precipitates adopt a preferred crystallographic orientation within the InN matrix, and show a characteristic diameter of ∼5 nm with an average distance of ∼500nm. The results suggest the effective solubility of O in InN could be below 1 at.% at 500°C. |
