Organometallic vapor-phase epitaxial thin films, with the (001) plane parallel to the surface of (110) sapphire substrates, were studied by using X-ray diffraction methods. The line profiles of the thin films along the [001] direction could be quantitatively reproduced by assuming the existence of a strained lattice at the interface. The deformation and growth faults were determined to be equivalent, and each amounted to 0.2%. Least-squares refinement of 42 independent peaks, after correcting for first-order thermal diffuse scattering, furnished the Debye-Waller factors for Ga and N atoms. The wurtzite positional parameter for the GaN thin film was found to be 0.3730. This was 1% smaller than that (0.377) for a strain-free single crystal, and the difference was attributed to strain effects.

X.Xiong, S.C.Moss: Journal of Applied Physics, 1997, 82[5], 2308-11