1. Department of Applied Physics; Stanford University; Stanford CA 94305 USA
2. Faculty of Fundamental Problems of Technology; Wroclaw University of Science and Technology; Wybrzeże Wyspiańskiego 27 Wrocław PL-50370 Poland
3. Faculty of Microsystem Electronics and Photonics; Wroclaw University of Science and Technology; Janiszewskiego 11-17 Wrocław PL-50372 Poland
4. Institute of High-Pressure Physics; Polish Academy of Sciences; Sokołowska 29/37 Warsaw PL 01142 Poland
5. TopGaN Sp. z o.o.; Sokołowska 29/37 Warsaw PL-01142 Poland