Structural and surface topography analysis of AlN single crystals grown on 6H-SiC substrates

摘要

Bulk A1N 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 measure ments. 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.