1. College of Physics, MIIT Key Laboratory of Aerospace Information Materials and Physics, Key Laboratory for Intelligent Nano Materials and Devices, Nanjing University of Aeronautics and Astronautics, No. 29 Jiangjun Road, Nanjing 211106, China
2. Innovation Center for Gallium Oxide Semiconductor (IC-GAO), College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China