Ultrathin MgO diffusion barriers for ferromagnetic electrodes on GaAs(001)

Ultrathin MgO(100) films serving as a diffusion barrier between ferromagnetic electrodes and GaAs(001) semiconductor templates have been investigated. Using Fe as an exemplary ferromagnetic material, heterostructures of Fe/MgO/GaAs(001) were prepared at 200 °C with the MgO thickness ranging from 1.5 to 3 nm. Structural characterization reveals very good crystalline ordering in all layers of the heterostructure. Auger electron spectroscopy depth-profiling and cross-sectional high-resolution transmission electron microscopy evidence diffusion of Fe into MgO and-for too thin MgO barriers-further into GaAs(001). Our results recommend a MgO barrier thickness larger than or equal to 2.6 nm for its application as a reliable diffusion barrier on GaAs(001) in spintronics devices.