1. Department of Electrical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand
2. Thai Microelectronics Center (TMEC), Chachoengsao 24000, Thailand
3. National Electronics and Computer Technology Center, Pathum Thani 12120, Thailand
4. Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
5. Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand