Hexagonal c-axis GaN layers grown by metalorganic vapor-phase epitaxy on Si(0Â 0Â 1)

We report on the epitaxial growth of hexagonal c-axis GaN on Si(0 0 1) substrates by metalorganic vapor-phase epitaxy (MOVPE). High-temperature (HT) AlN buffers were used. The use of 4° misoriented Si(0 0 1) substrates allows the growth of GaN layers with a single crystal orientation and low roughness and mosaïcity. Coalescence of the GaN films is obtained for thicknesses of about 1 μm. Crystal quality, strain state, polarity, and optical properties, assessed by transmission electron microscopy, X-ray diffraction and photoluminescence, are discussed and compared with those of GaN layers grown on Si(1 1 1) substrates.