We succeeded in measuring the density and direction of the edge component of threading dislocations (TDs) in c-plane (0001) GaN by micro-Raman spectroscopy mapping. In the micro-Raman spectroscopy mapping of the E2H peak shift between 567.85 and 567.75 cm−1, six different contrast images are observed toward directions of . By comparing X-ray topography and etch pit images, the E2H peak shift is observed where the edge component of TDs exists. In contrast, the E2H peak is not observed where the screw component of TDs exists.

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The threading edge dislocations in a GaN crystal are analyzed via micro-Raman spectroscopy mapping. A clear contrast image of the peak shift from a higher wavenumber to a lower wavenumber is simulated. The direction from the higher-wavenumber region to the lower-wavenumber region is found to be in the 90° rotation from the Burgers vector. The Burgers vector is experimentally determined to be using transmission electron microscopy. The magnitude of the Burgers vector agrees well between the simulated and experimental results. Thus, the density, direction, and magnitude of the edge component of the threading dislocations are identified using Raman spectroscopy mapping.

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An in-situ X-ray topography system using monochromatic synchrotron radiation for the observation of the stacking faults in 4H-SiC during a high-temperature annealing process was developed. We demonstrated that the stacking faults in nitrogen-doped 4H-SiC not only expand but also shrink at high temperatures. Furthermore, it was confirmed that the types of the core structure of partial dislocations enclosing the stacking fault can be determined at high temperatures.

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Residual contrast of threading edge dislocations is observed in synchrotron back-reflection X-ray topographs of 4H-SiC epitaxial wafers recorded using basal plane reflections where both g · b = 0 and g · b × l = 0. The ray-tracing simulation method based on the orientation contrast formation mechanism is applied to simulate images of such dislocations by applying surface relaxation effects. The simulated contrast features match the observed features on X-ray topographs, clearly demonstrating that the contrast is dominated by surface relaxation. Depth profiling indicates that the surface relaxation primarily takes place within a depth of 5 µm below the surface.

We achieved the growth of extremely-high quality SiC crystal with two-step solution method with specially-designed seed crystals. The two-step growth consists of 1st step growth on Si-face for the reduction of threading dislocations and 2nd step growth on C-face for the reduction of basal plane dislocations and thickening. In this method, we can make the dislocation density extremely low, while the polytype easily changes during growth due to the absence of spiral hillocks originating from threading screw dislocation (TSD). In this study, we prepared specially designed seed crystals for both 1st and 2nd growth steps to provide steps continuously. In the seeds, a few TSDs exist at the upper-side of the step structure. Consequently, we demonstrated the suppression of the polytype transformation during the C-face growth with extremely low-dislocation-density crystal. Accordingly, we successfully obtained extremely low-dislocation density 4H-SiC with TSD, TED and BPD density of 11, 385 and 28 cm-2.