1. Centre for Energy Research Institute for Technical Physics and Materials Science Konkoly-Thege M. út 29-33. 1121 Budapest Hungary
2. Consiglio Nazionale delle Ricerche Istituto per la Microelettronica e Microsistemi Strada VIII, n. 5, Zona Industriale I-95121 Catania Italy
3. Division of Semiconductor Materials Department of Physics Chemistry and Biology (IFM) Linköping University SE-58183 Linköping Sweden