1. Department of Semiconductor Materials Engineering Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 Wroclaw 50‐370 Poland
2. Department of Applied Physics and Ginzton Laboratory Stanford University 348 Via Pueblo Mall Stanford CA 94305 USA
3. Lukasiewicz Research Network – Institute of Electronic Materials Technology Wolczynska 133 Warsaw 01‐919 Poland
4. Faculty of Materials Science and Engineering Warsaw University of Technology Woloska 141 Warsaw 02‐507 Poland
5. Institute of Physics Polish Academy of Science al. Lotników 32/46 Warsaw 02‐668 Poland