1. Institute of Materials and Systems for SustainabilityNagoya University Furo-cho, Chikusa-ku Nagoya 464-8601 Japan
2. Center for GaN Characterization and AnalysisNational Institute for Materials Science 1-1 Namiki Tsukuba 305-0044 Japan
3. Department of Electrical Engineering and Computer ScienceNagoya University Furo-cho, Chikusa-ku Nagoya 464-8603 Japan
4. Aichi Synchrotron Radiation CenterAichi Science & Technology Foundation 250-3 Minamiyamaguchi-cho 489-0965 Seto Japan
5. Akasaki Research CenterNagoya University Furo-cho, Chikusa-ku Nagoya 464-8603 Japan
6. Venture Business LaboratoryNagoya University Furo-cho, Chikusa-ku Nagoya 464-8603 Japan