Molecular Beam Epitaxy of Fe$_{3}$Ga/Ga$_{1-x}$Al$_{x}$As Heterostructures: Growth, Properties and Spin Transport

Single crystal Fe$_{3}$Ga thin films have been grown on Ga$_{1-x}$Al$_{x}$As (001) by molecular beam epitaxy. The films are found to be pseudomorphic on Ga$_{1-x}$Al$_{x}$As and grow in a tetragonally-distorted Heusler-like D0$_{3}$ crystal structure. The Fe$_{3}$Ga films are ferromagnetic above room temperature with a saturation magnetization of 1200 emu/cm$^{3}$. They exhibit a perpendicular magnetic anisotropy due to the strain-induced tetragonal distortion. Rutherford backscattering spectrometry finds no interfacial reactions of Fe$_{3}$Ga/GaAs heterostructures, suggesting that Fe$_{3}$Ga is thermally stable on GaAs. Spin injection from Fe$_{3}$Ga into GaAs has been assessed by using Fe$_{3}$Ga/Ga$_{1-x}$Al$_{x}$As spin light-emitting diode (LED) structures. A steady-state spin polarization of 20{\%} is obtained at 2K. The bias dependence of spin injection is found to be very similar to that of Fe/Ga$_{1-x}$Al$_{x}$As spin LEDs [1]. This work was supported in part by ONR and NSF-MRSEC. [1] C. Adelmann \textit{et al.}, Phys. Rev. B \textbf{71}, 121301 (2005).