1. Department of Electrical and Computer Engineering, University of Washington, Seattle, Washington 98195, United States
2. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
3. Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China
4. Key Laboratory of Photoelectric Detection Materials and Devices of Zhejiang Province, Ningbo 315211, China
5. Department of Physics, University of Washington, Seattle, Washington 98195, United States