1. Chair of Electron Devices, University of Erlangen-Nuremberg, Cauerstrasse 6, 91058 Erlangen, Germany
2. Fraunhofer Institute for Integrated Systems and Device Technology, Schottkystrasse 10, 91058 Erlangen, Germany
3. Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská Cesta 9, 84104 Bratislava, Slovakia
4. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
5. Department of Materials Science and Engineering, and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea
6. Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria