Refraction high-energy diffraction (RHEED) patterns of GaN layers during the growth by metalorganic molecular beam epitaxy using (0001)6H-SiC and metalorganic vapor phase epitaxy grown Al0.05Ga0.95N/(0001)6H-SiC as substrates are observed. The patterns in initial growth are different for the GaN layers grown on 6H-SiC substrate and AlGaN template. The in-plane lattice constants of grown GaN layers estimated the duration of RHEED patterns are also discussed. (C) 2003 American Vacuum Society.