1. Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020, Japan.
2. Department of Electronics and Information Engineering, Hokkai-Gakuen University, Sapporo, Hokkaido 064-0926, Japan.
3. Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
4. Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.