1. Department of Electrical and Computer Engineering, The University of Utah, Salt Lake City, Utah 84112, USA
2. Terahertz Materials Analysis Center and Competence Center for III-Nitride Technology C3NiT-Janzén, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE 58183, Sweden
3. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
4. Department of Material Science and Engineering, The University of Utah, Salt Lake City, Utah 84112, USA
5. Leibniz-Institut für Kristallzüchtung, Berlin, e.V., Berlin 12489, Germany
6. Leibniz Institut für Polymerforschung e.V., 01069 Dresden, Germany