Cross-sectional X-ray microdiffraction study of a thick AlN film grown on a trench-patterned AlN/α-Al2O3 template

X-ray microdiffraction (XRMD) measurements using the AlN 22¯01 and 12¯10 Bragg reflections were performed to determine the cross-sectional distribution of local residual strain and twisting of crystal domains for a thick AlN film grown on a trench-patterned AlN/α-Al2O3 template. The distribution of the strain components in the [0001] and [112¯0] directions, which are perpendicular to the trench lines, was strongly influenced by the presence of voids caused by the trench pattern. The strains in the [11¯00] and [112¯0] directions determined using the two Bragg reflections were found to be significantly different, and this was shown to be the result of twisting of the crystal domains about the [0001] axis under the influence of anisotropic shear stress in the prismatic planes.