Microstructure Analysis of GaN Epitaxial Layers During Ion Implantation Using Synchrotron X-Ray Topography

Abstract

A study on characterization of microstructures in ammonothermal grown GaN wafers at different stages of device fabrication is conducted using synchrotron monochromatic beam X-ray topography (SMBXT), synchrotron X-ray rocking curve topography (SXRCT) as well as high resolution X-ray diffraction (HRXRD). Synchrotron monochromatic beam X-ray topographs reveal the various dislocation types and their distribution in the GaN wafer at different processing stages remains the same except that the contrast of threading dislocations is enlarged or darkened. HRXRD spectra of the ion implanted wafer reveals satellite peak and fringes from lattice damage. Rocking Curve Analysis by Dynamical Simulation (RADS) that fits the spectra gives a depth profile of strain correlated well to the designed implantation profile. This damage is completely healed after annealing process at 1225 ℃. Strain and tilt maps generated from SXRCT show an improvement in lattice bending level during annealing.