Synchrotron X-ray diffraction characterization of the inheritance of GaN homoepitaxial thin films grown on selective growth substrates

The crystallinity of one n-GaN (Si-doped) and two p-GaN (Mg-doped) homoepitaxial thin films selectively grown on GaN substrates was evaluated by using synchrotron X-ray diffraction. A reflection-mode monochromatic X-ray topography image from the n-GaN homoepitaxial thin film shows a mesh-shape structure that is similar to that of the selective-growth GaN substrate. Moreover, transmission-mode white-beam X-ray topography images from the GaN substrate and the n-GaN homoepitaxial thin film show similar regular dot-shape diffraction patterns. This suggests that, following hydride vapor phase epitaxy, the structural characteristics of the selectively grown GaN substrates inherited from their corresponding foreign substrates (dot-patterned sapphire) were inherited by the subsequent n-GaN homoepitaxial thin film, although the crystal quality of the homoepitaxial thin film had been deteriorated. White-beam topography images from two p-GaN homoepitaxial thin films grown on the same GaN substrate wafer and cut from adjacent areas indicate that the p-GaN thin films were non-uniform.