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.
Effect of low-temperature annealing on the electronic-and band-structures of (Ga,Mn)As epitaxial layers J. Appl. Phys. 115, 012009 (2014) We study the effect of low-temperature post growth annealing on the Fe layer in an epitaxial Fe/ GaAs(001) heterojunction. High resolution X-ray diffraction and X-ray reflectivity were used to probe the Fe layer before and after annealing. No change in morphological features like annealing induced intermixing and thickness variation of the Fe layer are observed. However, annealing leads to increase in the compressive strain and improves isotropy of the ferromagnetic layer as revealed by measuring both lateral and out-of-plane lattice components. Published by AIP Publishing.
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