We report on the structural in-plane anisotropy of GaN films grown on -plane sapphire substrates by metal organic chemical vapor deposition. It is found that GaN:Si grown on -face sapphire exhibits a strongly anisotropic wafer bending in the two orthogonal in-plane directions, with a larger curvature along the -axis of sapphire than along the -axis. Using a model developed for an elastically anisotropic bilayer structure and using our curvature data, the anisotropic biaxial stresses in the two in-plane directions have been estimated as and along parallel and perpendicular to -axis of sapphire, respectively. This anisotropic stress is also responsible for the distortion of the GaN hexagonal basal plane, as evidenced by x-ray diffraction measurements. The broadening of full width at half maximum of the GaN (0002) x-ray reflections varies with different azimuthal angles, correlated with the tilt of the -axis of GaN. The in-plane epitaxial relationships between the GaN (0001) and -face sapphire are found as -axis of GaN aligned with -axis of sapphire and -axis of GaN aligned with -axis of sapphire.
In-plane anisotropy characteristics of GaN epilayers grown on -face sapphire substrates
Hyonju Kim-Chauveau, Philippe De Mierry, Hugues Cabane, Dave Gindhart; In-plane anisotropy characteristics of GaN epilayers grown on -face sapphire substrates. J. Appl. Phys. 1 December 2008; 104 (11): 113516. https://doi.org/10.1063/1.3033370
Download citation file: