1. Institute of Semiconductor Technology and Laboratory for Emerging Nanometrology, Braunschweig University of Technology, 38092 Braunschweig, Germany
2. Epitaxy Competence Center ec2, Hans-Sommer-Straße 66, 38106 Braunschweig, Germany
3. Leibniz Institute for Crystal Growth, Max-Born-Straße 2, 12489 Berlin, Germany
4. Osram Opto Semiconductors GmbH, Leibnizstraße 4, 93055 Regensburg, Germany