1. Materials and Nano
Physics Department, KTH − Royal Institute of Technology, Kista, Stockholm, 16440, Sweden
2. State
Key Laboratory for Superlattices and Microstructures, Institute of
Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
3. Renewable and Sustainable
Energy Institute, University of Colorado, Boulder, Colorado 80309, United States