Influence of implanted Mg concentration on defects and Mg distribution in GaN
Ashutosh Kumar, Wei Yi, Jun Uzuhashi, Tadakatsu Ohkubo, Jun Chen, Takashi Sekiguchi, Ryo Tanaka, Shinya Takashima, Masaharu Edo, K. Hono
Abstract
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.