Application of synchrotron X-ray topography to characterization of ion implanted GaN epitaxial layers for the development of vertical power devices

Ion implantation is an essential step for selective area p-type doping of GaN, which is required for the development of vertical GaN devices that will help realize the potential of wide bandgap semiconductor GaN in power electronics. Changes to the microstructure of GaN epilayers on ion implantation and subsequent annealing were characterized by synchrotron X-ray topography and high-resolution X-ray diffraction (HRXRD). Enlarged contrast of screw and edge types of threading dislocations (TDs) on X-ray topographs after homoepitaxial growth is likely due to interaction of the dislocations with point defects. X-ray topographs reveal ion implantation does not change the distribution of dislocations in the wafer. HRXRD spectra have satellite peaks from lattice damage due to implantation. This damage is completely healed upon annealing. Strain and tilt maps derived from X-ray rocking curve topographs also show that annealing leads to an improvement in lattice bending.