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 MRAM s compatible with existing memory technology. Ferromagnet-semiconductor con tacts play a crucial role in all structures where spin injection into semic onductors is involved. We have investigated the properties of Co contacts o n InAs, the latter being known for its tendency to form Schottky barrier-fr ee ohmic contacts to metals. Co layers of different thicknesses have been d eposited by thermal evaporation. The macroscopic magnetization has been stu died using SQUID magnetometry. Structural properties and intermixing have b een investigated by nuclear magnetic resonance spectroscopy. Patterned Co c ontacts have been characterized by I/V measurements at different temperatur es. 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 60 K. (C) 1999 Elsevier Science B.V. All rights reserved.