1. Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
2. GlobalWafers Japan Co., Ltd., Seirou, Niigata 957-0197, Japan
3. Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
4. Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
5. Department of Electrical Engineering and Electronics, Kyushu Institute of Technology, Kitakyushyu 804-8550, Japan
6. Toshiba Corporation, Yokohama 225-8522, Japan