 Rau studied physics at the University of Tübingen, Germany, and the Université Claude Bernard, Lyon.Both his diploma thesis (1987) and his doctoral thesis (1991) were obtained for work performed in the group of Huebener, at the University of Tübingen, on the breakdown of Germanium under high magnetic fields, and for non-linear charge transport in semiconductors.He then moved to the Max Planck Institute for Solid State Physics in Stuttgart, where he first did work on crystalline silicon solar cells.