Molecular beam epitaxial growth of ferromagnetic Heusler alloys for group-IV semiconductor spintronic devices

Our recent progress in low-temperature molecular beam epitaxy of ferromagnetic Heusler alloys on group-IV-semiconductor is reviewed. By optimizing beam flux ratio (Fe:Si = 3:1) and growth temperature (130 °C), a high-quality hybrid structure, i.e., DO3-type Fe3Si on Ge with an atomically flat interface, was achieved. Excellent magnetic properties with a small coercivity (0.9 Oe) and electrical properties with Schottky barrier height of 0.52 eV were obtained. The ratio of the on-current to the off-current of Schottky diode was on the order of 104. In addition, heteroepitaxy of half-metallic alloys (Fe3 − XMnxSi(X = 0.6–1.4)) on Ge substrates was demonstrated. These results will be a powerful tool to open up group-IV-semiconductor spin-transistors, consisting of Ge channel with high mobility and ferromagnetic source/drain for spin-injection.