1. Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA 22904, USA.
2. School of Electronic Engineering, Soongsil University, Seoul 06938, South Korea.
3. Department of Intelligent Semiconductors, Soongsil University, Seoul 06978, South Korea.
4. Department of Material Science and Engineering, University of Virginia, Charlottesville, VA 22904, USA.