1. V. Lashkaryov Institute of Semiconductors Physics, National Academy of Sciences of Ukraine, Kyiv 03028, Ukraine
2. Taras Shevchenko National University of Kyiv, 64 Volodymyrs’ka St., 01601 Kyiv, Ukraine
3. Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany
4. Center for Materials, Architectures, and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, D-09107 Chemnitz, Germany
5. L.V. Pysarzhevsky Institute of Physical Chemistry, National Academy of Science of Ukraine, 03028 Kyiv, Ukraine
6. Forschungszentrum Jülich GmbH, Helmholtz-Institut Erlangen Nürnberg für Erneuerbare Energien (HI ERN), Immerwahrstr. 2, 91058 Erlangen, Germany