Characterization of GaN epitaxial layers on SiC substrates with AlxGa1−xN buffer layers

High quality GaN epitaxial layers were obtained with AlxGa1−xN buffer layers on 6H–SiC substrates. The low-pressure metalorganic chemical vapor deposition (LP-MOCVD) method was used. The 500 Å thick buffer layers of AlxGa1−xN (0≤x≤1) were deposited on SiC substrates at 1025°C. The FWHM of GaN (0004) X-ray curves are 2–3 arcmin, which vary with the Al content in AlxGa1−xN buffer layers. An optimum Al content is found to be 0.18. The best GaN epitaxial film has the mobility and carrier concentration about 564 cm2 V−1 s−1 and 1.6×1017 cm−3 at 300 K. The splitting diffraction angle between GaN and AlxGa1−xN were also analyzed from X-ray diffraction curves.