1. Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan
2. Department of Electronics Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan
3. International College of Semiconductor Technology, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan