1. Microelectronics Research Unit
2. Faculty of Information Technology and Electrical Engineering
3. University of Oulu
4. FI-90014 Oulu
5. Finland
6. Institute of Solid State Physics
7. University of Latvia
8. LV-1063 Riga
9. Latvia
10. Max Planck Institute for Solid State Research
11. Institute of Physics of the Czech Academy of Sciences
12. 18221 Prague
13. Czech Republic