Spin injection in FM/2DEG/FM structures in high-quality In0.75Ga0.25As/In0.75Al0.25As inverted HEMTs

We here investigated spin injection in the top- and side-electrode spin-valve devices using In0.75Ga0.25As/In0.75Al0.25As inverted-HEMTs grown on GaAs substrates via InAlAs step graded-buffer. These HEMTs have the electron mean free paths of View the MathML source and Rashba spin orbit coupling constants, α>16 (View the MathML source) in their 2DEG channels. In the top-electrode devices, we observed dependency of the spin-valve signal on the Ni50Fe50 electrode spacing, D. The resistance variation ratio, ΔR/RP, in the top-electrode devices reached up to ∼1%, while that in the side-electrode devices remains as high as 0.2%. This value of ΔR/RP∼1% corresponds to the spin injection efficiency of ∼7.5%, which is one of the highest value obtained in this type of samples.