1. Research Institute for Advanced Electronics and PhotonicsNational Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki Japan
2. GaN Advanced Device Open Innovation LaboratoryNational Institute of Advanced Industrial Science and Technology (AIST) Nagoya Aichi Japan
3. Center for Low‐temperature Plasma SciencesNagoya University Nagoya Aichi Japan
4. Faculty of Science and TechnologyMeijo University Nagoya Aichi Japan
5. Advanced Manufacturing Research InstituteNational Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305‐8564 Japan