Observation of strongly enhanced inverse spin Hall voltage in Fe₃Si/GaAs structures

We performed spin pumping experiment on high quality, epitaxial Fe₃Si/GaAs structures grown by molecular beam epitaxy. By tailoring the thickness and doping (n, p) level of the conducting GaAs epi-layer, thermal heating common of ferromagnetic metal/semiconductor heterostructure was removed effectively. A large inverse spin Hall Effect (ISHE) voltage up to 49.2 μV was observed for Fe₃Si/p-GaAs. Smaller ISHE voltage (V_ISHE) by a factor of ∼0.4 was obtained for Fe₃Si/n-GaAs, as scaled with its resistivity. By taking into account of the “self-induced” ISHE apparently observed in our samples, the minimum value of spin Hall angle θ_ISHE for n-GaAs and p-GaAs was estimated to be 1.9 × 10⁻⁴ and 2.8 × 10⁻⁵, respectively.