High crystalline quality epitaxial GaN films with thicknesses 0.5-1.5
mu m have been successfully grown directly on Al2O3(0001) substrate by
pulsed laser deposition (PLD). For films grown at 950 degrees C, we o
btained an x-ray diffraction rocking curve linewidth of 7 are min. The
ion channeling minimum yield in the near-surface region (similar to 2
000 Angstrom) for a 0.5 mu m thick film was similar to 3%-4% indicatin
g a high degree of crystallinity, The optical absorption edge measured
by UV-visible spectroscopy Miss sharp. and tbe band gap was found to
be 3.4 eV. The crystalline properties of these PLD GaN films are compa
rable to those grown by metalorganic chemical vapor deposition and mol
ecular beam epitaxy. (C) 1997 American Institute of Physics.