1. Laboratory
for Solid State Physics, ETH Zurich, Otto-Stern-Weg 1, CH-8093 Zurich, Switzerland
2. L-NESS
and Department of Physics, Politecnico di Milano, Via Anzani 42, I-22100 Como, Italy
3. Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
4. Institute
of High Pressure Physics, Polish Academy of Sciences, ul. Sokolowska
29/37, 01-142 Warszawa, Poland
5. TopGaN sp. z.o.o., al. Prymasa
Tysiąclecia 98, 01-424 Warszawa, Poland
6. Electron
Microscopy Center EMPA, Swiss Federal Laboratories for Materials Science and Technology, Uberlandstrasse
129, CH-8600 Dübendorf, Switzerland
7. L-NESS
and Department of Materials Science, Università di Milano-Bicocca, Via
Cozzi 55, I-20125 Milano, Italy