1. CNR-IMM, Strada VIII, 5, 95121 Catania, Italy
2. GREMAN, UMR 7347, Université de Tours, CNRS, 37071 Tours, France
3. Department of Electronic Science and Engineering, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
4. NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135, USA
5. Department of Electrical and Photonics Engineering, Technical University of Denmark, Ørsteds Plads, Building 343, DK-2800 Kgs. Lyngby, Denmark
6. CNR-IMM, 40129 Bologna, Italy
7. Electrical Engineering Department, University of South Florida, 4202 E. Fowler Avenue, ENG 030, Tampa, FL 33620, USA
8. INFN-LNS, Via Santa Sofia 62, 95124 Catania, Italy