Interfacial crystal structures and non-local spin signals of Co₂FeAl_0.5Si_0.5/n-GaAs junctions

We have investigated interfacial crystal structures and non-local spin signals ΔR of Co₂FeAl_0.5Si_0.5 (CFAS)/n-GaAs junctions. Cross-sectional transmission electron microscopy observations indicated that with the exception of Ga diffusion into CFAS of the sample deposited at 400 °C, the interfacial structure of the junctions and defect density at the interface were not very different for different CFAS fabrication temperatures of the substrate (TCFAS). The obtained reflection high-energy electron diffraction patterns showed that all samples fabricated at TCFAS varying from room temperature to 400 °C exhibited the L2₁ ordered structure in the vicinity of CFAS/n-GaAs junctions. It is found that the junctions with larger rectifying characteristic as indicated by the conduction ratio G(0.5 V)/G(-0.5 V) show larger spin signal ΔR. This may strongly affect the spin injection/detection efficiency.