Dopant-defect interactions in Mg-doped GaN via atom probe tomography

In this work, an in-depth analysis of atomic level dopant-defect interactions in N-polar GaN:Mg was performed using atom probe tomography (APT). The 3D visualization of ion distribution revealed the formation of spherical Mg-rich clusters and the segregation of Mg dopant toward dislocations in MOCVD-grown GaN:Mg. Impurities, such as oxygen and hydrogen, were identified and detected adjacent to Mg-rich dislocations. Crystal stoichiometry around the defect regions was investigated to understand how the defects can influence dopant diffusion. Non-stoichiometric regions of N:Ga were found adjacent to Mg-rich dislocations and overlapping with some Mg-rich clusters, indicating dopant-defect interplay. Variations in N:Ga were not proportional to the Mg content, suggesting that the micro-features (clusters and dislocations) interact differently with local chemistry. Techniques for defining the quality of an APT experiment through invalidation of artifacts are also demonstrated. Mg-rich defects and variations in N:Ga were found to be independent of artifacts related to the evaporation field in APT.