Synchrotron X-ray Topography Characterization of Commercial GaN Substrates for Power Electronic Applications

Abstract

Commercial GaN substrates from different vendors were characterized by synchrotron X-ray topography (XRT) as well as high resolution X-ray diffraction (HRXRD) to evaluate their defect and strain distributions. Synchrotron monochromatic beam X-ray topographs reveal the various dislocation types and their distribution in the GaN materials grown by different methods. By correlating the dislocation contrast with ray-tracing simulation results, the Burgers vectors of dislocations were successfully determined. The ammonothermal-grown GaN material using native seed show the highest quality with low dislocation densities. Patterned HVPE GaN wafers have heterogeneous distribution of dislocations with large areas of low threading dislocation densities. Regular HVPE GaN substrate and ammonothermal GaN grown on an HVPE GaN seed show a very high level of strain, and the dislocation densities are much higher than ammonothermal and patterned HVPE samples.