The results of GaN epitaxial crystal growth on 4° off-axis Si- and C-face 4H-SiC without buffer layers by tri-halide vapor-phase epitaxy (THVPE) with high-speed wafer rotation and the properties of the obtained material are briefly described in this paper. GaN epitaxial layers were grown on 4° off-axis 4H-SiC(0001)Si and 4H-SiC(000-1)C substrates. The obtained material’s properties were studied by Nomarski optical microscopy, scanning electron microscopy, photoluminescence, surface two-photon excitation microscopy, X-ray diffraction and Raman spectroscopy. The structural and optical properties of the GaN epitaxial layer are presented and discussed. By adopting an external GaCl3 material supply system, high-speed rotation was applicable, and its effect was confirmed. The results show that when THVPE was used under growth pressure of 600 mbar at 900 °C–950 °C, the surface reaction rate was sufficiently high, and the GaN epitaxial layer was grown under conditions of controlled raw-material supply rates. High growth rates (40–50 μm h−1) and relatively low threading dislocations (~7 × 107 cm−2) were achieved on 4° off 4H-SiC(000-1)C despite the large lattice mismatch (3.1%) between SiC and GaN and without any buffer layers by introducing step flow growth and growth on a high-quality 4H-SiC substrate. We found that epitaxial layers with a smooth surface morphology can be grown on 4H-SiC(000-1)C compared with growth on 4H-SiC(0001)Si.
Source:IOPscience
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