1. Department of Physics and Department of Electrical and Electronics Engineering, UNAM−Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
2. Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
3. Clippinger Research Laboratories, Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, United States