2Terahertz Materials Analysis Center and Competence Center for III-N Technology, C3NiT—Janzèn, NanoLund and Solid State Physics, Lund University, 22100 Lund, Sweden
3Wallenberg Initiative Materials Science for Sustainability (WISE), Department of Physics, Lund University, 22100, Lund, Sweden
5Competence Center for III-N Technology, C3NiT—Janzèn, Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
6Wallenberg Initiative Materials Science for Sustainability (WISE), Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden