Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 23: Spinelectronics/ Spininjection in Heterostructures

MA 23.6: Vortrag

Mittwoch, 27. Februar 2008, 18:00–18:15, H 1028

Room temperature operation of a magnetic tunnel transistor with an epitaxial spin valve base — Alexander Spitzer, •Julien Vigroux, Juergen Moser, and Guenther Bayreuther — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg, 93040, Germany

We present a magnetic tunnel transistor (MTT) with room temperature operation. The performance of MTTs is usually limited to temperatures far below 300K due to strongly temperature dependent leakage currents of the Schottky barrier. These leakage currents originate from defects created by Ar-sputtering processes during patterning of the MTT. The leakage currents dominate the collector current IC and therewith reduce the magneto current ratio (MCR) which is the normalized difference in IC for parallel and antiparallel alignment of the ferromagnetic layers in the MTT. To overcome this hurdle, two approaches are possible: The use of either wet chemical etching to remove those defects or film deposition through shadow masks. We show that both lead to a strong reduction of the leakage current. As a base contact for our MTT we use a fully epitaxial FeCo/Au/FeCo spin valve grown on n-GaAs(001). A Ta emitter grown on an Al2O3 tunnel barrier provides the hot electron emitter current IE. Depending on the thickness of the magnetic layers our MTTs show MCRs over 1000 % at 11K. Support by Deutsche Forschungsgemeinschaft (SFB 689) and Marie Curie RTN "ultrasmooth" is gratefully acknowledged.