Influence of implanted Mg concentration on defects and Mg distribution in GaN

Efficient acceptor activation in gallium nitride (GaN) achieved through Mg ion-implantation depends mainly on the concentration of implanted Mg ions and the post-implantation annealing process. In this study, we conducted correlative scanning transmission electron microscopy, atom probe tomography, and cathodoluminescence (CL) measurements on Mg-implanted GaN layers with the implanted concentration ranging from 1 × 1017 cm−3 to 1 × 1019 cm−3. It was found that at the implanted concentration of ∼1 × 1018 cm−3, Mg atoms were randomly distributed with defects likely to be vacancy clusters whereas at the implanted concentration of ∼1 × 1019 cm−3, Mg-enriched clusters and dislocation loops were formed. From the CL measurements, the donor–acceptor pair (DAP) emissions from the implanted and un-implanted regions are obtained and then compared to analyze Mg activation in these regions. In the sample with Mg ∼1 × 1019 cm−3, the existence of Mg-enriched clusters and dislocations in the implanted region leads to a weaker DAP emission, whereas the absence of Mg-enriched clusters and dislocations in the sample with Mg ∼1 × 1018 cm−3 resulted in a relatively stronger DAP emission.