1. Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, Nizhniy Novgorod 603087, Russia
2. Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 13 Lavrentiev av., Novosibirsk 630090, Russia
3. Laboratory of 2D Materials for Optoelectronics, Moscow Institute of Physics and Technology, 9 Institutsky lane, Dolgoprudny 141700, Russia