1. Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260, United States
2. Luminous! Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
3. Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
4. Department of Physics, St. Bonaventure University, St. Bonaventure, New York 14778, United States