Ferromagnet semiconductor hybrid structures

The fabrication of ferromagnet semiconductor hybrid structures in high crystal perfection is a prerequisite for spintronic device concepts. Our focus is on the growth of half-metallic Heusler alloys on GaAs-related structures. As an amendment, we investigate MgO interlayers at the Heusler alloy/GaAs interface as diffusion and spin-filtering barriers. The growth of these materials is the long-standing basis for spin transport and spin manipulation studies in the core research areas Nanoanalytics and Control of Elementary Excitations by Acoustic Fields.

In parallel, we pursue the preparation of fully crystalline thin film stacks consisting of a semiconducting channel sandwiched between two ferromagnetic layers. From such stacks, new vertical device types could be fabricated. In order to overcome the challenges associated with the growth of a semiconductor on a metal, we have developed solid-phase epitaxy as an approach where an amorphous film of Ge is deposited on Fe₃Si and then crystallized slowly by thermal annealing. The films prepared with this method crystallize in the well-oriented, layered tetragonal structure FeGe₂.

In addition, we focus on the preparation of single FeGe₂ films on GaAs and on graphene to study the properties of this new layered ferromagnetic material, which does not exist as a bulk material in this structure. This research direction acts as a bridge to Nanofabrication activities on 2D materials.