Cathodoluminescence and Atom Probe Study of Mg Diffusion and Activation along Threading Dislocations in Mg Implanted Homoepitaxial GaN

摘要

To realize precise p-type doping in vertical devices, Mg ion implantation is an important technique. At present, dislocations still remain in GaN substrate and epitaxial growth, the effect of dislocations on Mg diffusion and activation should also be explored. Recently, we have proposed a high spatially resolved cathodoluminescence (CL) imaging on the slanted cross-section of Mg implanted GaN epilayer, and Mg pipe diffusion through threading dislocations (TDs) have been found [1]. It is noted that some TDs exhibit enhanced Mg-related donor-acceptor pair (DAP) while the others not. In this work, we have carried out a comprehensive study on the interaction between TDs and Mg in Mg-imp homoepitaxial GaN layer. It includes optical characterization by CL focusing on the distribution of activated Mg, structural analysis of dislocation character based on etch pit and transmission electron microscope (TEM), and atomic distribution of Mg at different dislocations by atom probe tomography.