Improvement of crystal quality of AlN and AlGaN epitaxial layers by controlling the strain with the (AlN/GaN) multi-buffer layer

摘要

AlN and AlGaN epitaxial layers with Al composition of 0.6-0.8 were grown by low-pressure metal organic vapor phase epitaxy on a (0001) 6H-SiC substrate using the (AlN/GaN) multi-buffer layer structure (MBLS). Strain of the grown layer could be controlled by structure of the inserted (AlN/GaN) MBLS. It was found that the crystal quality of the grown layer could be improved with increase of the tensile strain in a-axis (compressive strain in c-axis): full-width at half-maximum (FWHM) of X-ray rocking curves (XRC) of both (0002) plane (ω scan) and (1012) plane (φ scan) were decreased from 1530 arcsec to 79 arcsec and 3962 arcsec to 853 arcsec for the AlN template, respectively. FWHM of the φ scan XRC was several times larger than that of the ω scan, though the former was roughly proportional to the latter.