Transport and magnetic properties of Fe/GaAs Schottky junctions for spin polarimetry applications

The electrical, magnetic and spin-filtering properties of Pd/Fe/GaAs(001) junctions are investigated. The Pd/Fe thin layers are deposited on GaAs(001) surfaces both clean and passivated by a thin oxide layer. The surface composition, structure and electronic properties of the starting surfaces are studied by means of XPS, LEED, EELS and photoreflectance. The Fe layer magnetic properties are characterized by magneto-optical Kerr effect (MOKE) measurements, while the electronic properties of the junctions are characterized by current-voltage (I-V) and photoreflectance measurements. For both types of substrate surfaces, the magnetization of the Fe layers is found close to that of a bulk Fe slice of equivalent thickness. For the oxide interface, the I-V curve exhibits almost an ideal Schottkylike behavior, since it can be very well interpreted by the thermoionic equation, using the ideality factor of n = 1.02 and surface barrier θ_b 0.7 eV. For junctions prepared on the reconstructed GaAs(001) surface, the ideality factor and barrier heights are found in the range of 1.06-1.2 and 0.60-0.75 eV, respectively. Both structures give rise to similar spin filter effects under injection of spin-polarized electrons.