Affiliation: | (1) Department of Physics and Quantum-functional Semiconductor Research Center, Dongguk University, 3-26 Pildong, Chungku, Seoul, 100-715, Korea;(2) Advanced Semiconductor Research Center, Division of Electrical and Computer Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, Korea |