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 1x10(17) cm(-3) to 1x10(19) cm(-3). It was found that at the implanted concentration of similar to 1x10(18) cm(-3), Mg atoms were randomly distributed with defects likely to be vacancy clusters whereas at the implanted concentration of similar to 1x10(19) 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 similar to 1x10(19) 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 similar to 1x10(18)cm(-3) resulted in a relatively stronger DAP emission.