Influence of thermal annealing on the spin injection and spin detection through Fe/GaAs interfaces

Abstract

A strong bias asymmetry of the spin-injection efficiency through an epitaxial Fe/GaAs Schottky tunnel contact is observed. Low-temperature post-growth thermal annealing is shown to strongly affect the spin-injection efficiency. The annealing leads either to a reduction or an enhancement. The spin accumulation is addressed electrically in a lateral spin-valve geometry using a non-local spin-valve setup at liquid helium temperatures. A spin-injection efficiency of up to 5.5% is estimated from experimental results. The electrical properties of the Schottky tunnel diode do not reflect the bias asymmetry and the changes in the spin-injection efficiency during annealing. Formation of spin-polarized interface states (IS) close to the Fermi-level is a possible explanation. The IS will not only radically affect the spin-injection but also the spin-detection process.

Role of Hydrogen Evolution during Epitaxial Electrodeposition of Fe on GaAs

“…1 For ferromagnetic bcc Fe, GaAs is a suitable substrate to achieve epitaxy because of the small lattice-misfit (1.4%). The research on epitaxial Fe/GaAs structures is of ongoing interest for injection and detection of spin polarized electrons, [2][3][4] and the study of magnetism in reduced dimensions and at interfaces. 5,6 For a long time, molecular beam epitaxy (MBE), was the preferred method for the fabrication of Fe/GaAs structures.…”

Effect of low-temperature post-growth annealing on anisotropic strain in epitaxial Fe layers deposited on GaAs(001)

“…6 Other reports also indicate a strong influence of post-growth annealing on spin injection efficiency. [7][8][9] We also observed a similar effect, 10 where the non-local spin signal was observed only after a soft post-annealing of the structures to 200 C. To date, several studies were attempted to correlate post growth annealing and spin injection by analyzing the atomic structure of the FM/SC interface. Zega et al proposed a model of ordered and coherently intermixed interface of Fe and As atoms.…”

“…Both the metal layers were deposited at room temperature. The sample layout designed for spin transport experiments 10 with nominal thicknesses is shown in Fig. 1.…”

Development of an optically gated Fe/n-GaAs spin-polarized transistor

“…In fact, for Si, it is shown that a very thin (70 nm) channel thickness led to a higher spin accumulation possibly due to the confinement of injected spins [25]. To eliminate further spurious sources of the field-dependent signals, nonmagnetic metals could be used as the source and the drain contacts for the non-local injection and detection [26]. As the key step to test the feasibility of the optical gating of the non-local spin transport, the circularly-polarised light at the 822 nm wavelength was illuminated to the region of pure spin current between the injector and the detector ferromagnets as shown in Fig.…”