1. Semiconductor Electronics Department, Lviv Polytechnic National University, 12 Bandera Str., 79013 Lviv, Ukraine
2. Department of Physical, Analytical and General Chemistry, Lviv Polytechnic National University, 12 Bandera Str., 79013 Lviv, Ukraine
3. Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
4. Department of Sensor and Semiconductor Electronics, Ivan Franko National University of Lviv, Tarnavskogo Str., 107, 79017 Lviv, Ukraine
5. Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
6. Physics Department, University of Oxford, Keble Rd., Oxford OX13 RH, UK