Cobalt contacts on indium arsenide

Spin-dependent transport in ferromagnet–semiconductor structures is a field of growing interest, driven by the possibility to realize solid-state MRAMs compatible with existing memory technology. Ferromagnet–semiconductor contacts play a crucial role in all structures where spin injection into semiconductors is involved. We have investigated the properties of Co contacts on InAs, the latter being known for its tendency to form Schottky barrier-free ohmic contacts to metals. Co layers of different thicknesses have been deposited by thermal evaporation. The macroscopic magnetization has been studied using SQUID magnetometry. Structural properties and intermixing have been investigated by nuclear magnetic resonance spectroscopy. Patterned Co contacts have been characterized by I/V measurements at different temperatures. Our data indicate a partial intermixing over several monolayers at the interface resulting in a thin layer with ferromagnetic properties. The I/V characteristics show low contact resistance and a linear behaviour down to 60K.