1. School of Electrical and Computer Engineering, University of Campinas 1 , 13083-852 Campinas-SP, Brazil
2. Center for Semiconductor Components and Nanotechnologies, University of Campinas 2 , 13083-870 Campinas-SP, Brazil
3. Institut für Mathematik und Naturwissenschaften, Fachhochschule Nordwestschweiz 3 , CH-5210 Windisch, Switzerland