A comparative study of epitaxy of AlN, GaN and their alloys, grown on c -axis and off-axis substrates of single-crystal aluminum nitride has been carried out. Growth on off-axis (>30°) substrates appears to result in rough surfaces and the absence of two-dimensional electron gas (2DEG). However, smooth morphologies were demonstrated for both homoepitaxial and heteroepitaxial growth on on-axis ( 2 /V s and a sheet density of 8.5×10 12 cm −2 at room temperature, was also demonstrated for the first time.
