Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Applied Physics Express  

Defect time-evolution was investigated in Mg ion-implanted GaN after annealing at 1573 K for an unprecedentedly long duration. Transmission electron microscopy directly revealed that annealing for over 30 min reduced defects inhibiting Mg activation, just like annealing at 1753 K for a short duration. The cathodoluminescence intensity of donor-acceptor pair originating from Mg acceptors increased as the duration increased, and the intensity after annealing for 60 min was higher than after short-duration annealing at 1753 K. These show the potential of lowering the annealing temperature by prolonging the duration, which would lead to practical annealing technology for Mg ion-implanted GaN.

DOI： 10.35848/1882-0786/abd308

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

Sputtering enables uniform and clean deposition over a large area, which is an issue with exfoliation and chemical vapor deposition methods. On the other hand, the process of physical vapor deposition (PVD) film formation has not yet been clarified. We prepared several samples from the sub-monolayer region, and performed Raman spectroscopy, X-ray photon spectroscopy and high-angle annular dark-field scanning transmission electron microscopy. From these results, the internal stresses inherent to PVD films, the bonding states specific to sub-monolayers, and the unique film structure and the grain formation process of PVD films were discussed from the perspective of sub-monolayers. As a conclusion, we found that it is important to suppress the formation of sub-monolayers on the substrate to completely form the first layer.

DOI： 10.35848/1347-4065/ac3fc9

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Applied Physics Express  

We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

DOI： 10.35848/1882-0786/ac481b

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/jmicro/dfaa070

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcc.9b05353