1. Electrical and Computer Engineering, Michigan State University, East Lansing, Michigan 48824, United States
2. National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Key Laboratory of Microelectronic Devices and Circuits (MOE), Institute of Microelectronics, Peking University, Beijing 100871, China
3. Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States