The growth kinetics of GaN/(00•1)sapphire hetero-epitaxial films were studied, at substrate temperatures ranging from 560 to 640C, by using reflection high-energy electron diffraction specular reflection intensity monitoring techniques. An alternating-element exposure growth method was used in which Ga and N atoms were supplied separately (rather than simultaneously as usual) to the substrate, with the insertion of a time delay between successive Ga-flux and N-flux exposures. A time-dependent recovery of the reflection high-energy electron diffraction specular reflection intensity, during the time delay, was associated with Ga-N surface molecule migration on Ga-terminated surfaces. The activation energy for this migration process was deduced to be 1.45eV.

H.Liu, J.G.Kim, M.H.Ludwig, R.M.Park: Applied Physics Letters, 1997, 71[3], 347-9