1. University of Siegen, School of Science and Technology,
Department of Electrical Engineering and Computer Science, Hölderlinstr. 3, 57076 Siegen, Germany
2. RWTH Aachen University, Faculty of Electrical
Engineering and Information Technology, Chair for Electronic Devices, Otto-Blumenthal-Str. 25, 52074 Aachen, Germany
3. Departmento
de Electrónica y Tecnología de Computadores, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada, Spain