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Sumathi, R. Radhakrishnan; Barz, Ralph-Uwe; Straubinger, T.; Gille, Peter (2012): Structural and surface topography analysis of AlN single crystals grown on 6H-SiC substrates. In: Journal of Crystal Growth, Vol. 360, No. 1: pp. 193-196
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Bulk AlN single crystals (3 mm thick and 1 in. diameter) were hetero-epitaxially grown on (0001) 6H-SiC substrates by the sublimation method. Double-crystal x-ray diffraction and micro-Raman results confirm the good crystallinity as well as structural homogeneity of the grown crystals. The presence of low-angle grain boundaries was observed by x-ray diffraction rocking curve analysis and also supported by defect-selective etching analysis. The estimated defect density of the 3 mm thick crystals is about (5-8)×10 5 cm -2. 3D-microstructures with different morphology were observed on the as-grown crystal surfaces and were interpreted to be originated from screw dislocations. These screw dislocations are decorated by carbon impurities as evidenced by micro-Raman spectroscopic measurements. SiC incorporation in the grown crystals was found to be fairly low with 4 mol\% at 2 mm distance from the interface and varies slightly between different sub-grains.