Local Lattice Plane Orientation Mapping of Entire GaN Wafer

We modified a synchrotron X-ray diffraction imaging, a kind of X-ray diffraction topography (XRDT), technique to visualize a local latticeplane shape of a whole wafer and to make measurement time shorter. The technique needs monochromatic X-rays with an enough large beam size having a small angular divergence. In addition, it has two limitations related to a local d spacing as well as a local lattice-plane curvature. Our key point is that two equivalent reflections or more for different sample azimuth angles have been used. We obtained center angles of rocking curves from many positions on a sample surface with a two-dimensional detector and evaluated the local deviation angles on two respective diffraction planes. Local reciprocal-lattice vectors for respective sample surface positions were obtained using the deviation angles via the rotation matrix. Our three following studies are introduced: 1)lattice-plane orientation mapping of homoepitaxial GaN (0001) thin films grown on a 2-inch whole wafer, 2)visualization of crystal perfection and lattice-plane shape of 4-inch whole GaN(0001) wafer, and 3)visualization of lattice-plane twisting of an m-planeGaN homoepitaxial layer. The developed XRDT technology allows us to quickly visualize variation of lattice-plane orientations in a whole GaN wafer as well as the anisotropic mosaicity.