1. Department of Electrical and Electronics Engineering Department of Physics, UNAM−Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
2. Department of Materials Science and Nanotechnology, Abdullah Gul University, Kayseri 38080, Turkey
3. LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays, Centre of Optical Fiber Technology, The Photonics Institute, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore