1. Center for Neuromorphic Engineering, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
2. Department of Material Science and Engineering, Korea University, Seoul 02841, Republic of Korea
3. Quantum Functional Semiconductor Research Center, Dongguk University, Joong-gu, Seoul 04620, Republic of Korea
4. Center for Optoelectronic Materials and Devices, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea