Large-area analysis of dislocations in ammonothermal GaN by synchrotron radiation X-ray topography

The large-area defect structure of high-quality ammonothermal GaN was studied by synchrotron radiation X-ray topography (SR-XRT) and high-resolution X-ray diffraction (XRD). The threading dislocation densities of mixed and screw dislocations were determined separately by SR-XRT and were 3.2 × 104 and 3.1 × 103 cm−2, respectively. Threading edge dislocations were not observed. SR-XRT images show that TMDs are clustered on a large scale and form short dislocation arrays with an average spacing between dislocations of 12 µm. XRD rocking curves were used to measure an average lattice tilt of 10 arcsec caused by the dislocation arrays.