1. Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
2. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
3. Infineon Technologies, Siemensstraße 2, 9500 Villach, Austria
4. Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
5. KAI GmbH, Europastraße 8, 9500 Villach, Austria
6. Infineon Technologies, Schottkystraße 10, 91058 Erlangen, Germany