1. Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
2. Kazan Federal University, Institute of Physics, 420008 Kazan, Russia
3. Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
4. Department of Electrical and Electronics Engineering, Department of Physics, UNAM − Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
5. Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore