1. Key Laboratory of Physical Electronics and Devices for Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics & Information Technology, Xi’an Jiaotong University, Xi’an 710049, China
2. School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China
3. Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, U.K.
4. School of Microelectronics, Xidian University, Xi’an 710126, China