1. Department of Micro and Nanosystems, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
2. Scania Tekniskt Centrum, 15148 Södertälje, Sweden
3. Department of Integrated Devices and Circuits, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, SE-164 40 Kista, Sweden
4. Faculty of Electrical Engineering and Information Technology, RWTH Aachen University, Otto-Blumenthal-Strsse 25, 52074 Aachen, Germany