1. International College of Semiconductor Technology, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2. Department of Materials Science & Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
3. Department of Electro-physics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
4. Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 10610, Taiwan
5. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
6. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States
7. Taiwan Semiconductor Research Institute, Hsinchu 30010, Taiwan