After studying physics, Andreas Waag joined the group of Prof. Landwehr at the Physics Institute at Würzburg. During his PhD thesis, he developed CdTe-CdMnTe heterostructures by molecular beam epitaxy, mainly focusing on the doping problem of these materials as well as the properties of semimagnetic heterostructures. During the habilitation, he worked on new materials for II-VI blue-green laser diodes. For this work, Andreas Waag received the Gaede Prize of the German Vacuum Society. After that, he joined the group of Prof. Gunshor at Purdue University, USA, further working on the optimisation of II-VI laser diodes. During the time at Würzburg University, the group of Andreas Waag was able to implement an electrical spin injection into a semiconductor for the first time. The respective Nature publication from 1999 is highly cited (more than 500 citations). One focus of the research work was the ferromagnetic material GaMnAs, including MBE growth, high magnetic field transport, electrical and magnetic characterisation of the material properties. During his time in Ulm, first projects concerning the development of oxide semiconductors for optoelectronics, magnetoelectronics and sensor applications were started. Since 2003, Andreas Waag is head of the institute of semiconductor technology (IHT) in the faculty of electrical engineering at the TU Braunschweig. At the IHT, intense activities have been started in order to further develop oxide semiconductors for different applications.