1. Department of Electrical and Electronics Engineering Department of PhysicsUNAM‐Institute of Materials Science and NanotechnologyBilkent University Ankara 06800 Turkey
2. LUMINOUS! Centre of Excellence for Semiconductor Lighting and DisplaysCentre of Optical Fiber TechnologyThe Photonics InstituteSchool of Electrical and Electronic EngineeringSchool of Physical and Mathematical SciencesNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore