1. Laboratory of Organic Electronics Department of Science and Technology (ITN) Linköping University Norrköping SE‐601 74 Sweden
2. Terahertz Materials Analysis Center (THeMAC) Department of Physics Chemistry and Biology (IFM) Linköping University Linköping SE‐581 83 Sweden
3. Center for III‐Nitride Technology C3NiT‐Janzèn Department of Physics Chemistry and Biology (IFM) Linköping University Linköping SE‐581 83 Sweden
4. Solid State Physics and NanoLund Lund University Lund S‐221 00 Sweden