1. Fraunhofer Institute for Applied Solid-State Physics (IAF), Tullastrasse 72, D-79108 Freiburg, Germany, ingmar.kallfass@iaf.fraunhofer.de
2. Fraunhofer Institute for Applied Solid-State Physics (IAF), Tullastrasse 72, D-79108 Freiburg, Germany
3. Sony Deutschland GmbH, Hedelfinger Strasse 61, D-70327 Stuttgart, Germany