Orientation selection and superconducting properties of epitaxial Al on ferromagnetic semiconductor (In,Fe)As
Superconductor/ferromagnet heterostructures provide a versatile platform for exploring spin-dependent superconducting phenomena arising from interfacial proximity effects. In this article, we investigate the structural and superconducting properties of Al thin films grown in situ by molecular beam epitaxy on strained Fe-doped ferromagnetic semiconductor (FMS) (In,Fe)As layers. X-ray diffraction and transmission electron microscopy reveal the epitaxial growth of single-crystalline Al layers, with the growth orientation changing from (110) to (111) as the in-plane lattice constant of (In,Fe)As increases. The superconducting critical temperature of Al varies systematically with the film surface morphology and grain size. In addition, the critical magnetic field of Al exhibits an anomalous decrease below 0.5 K, possibly reflecting magnetic coupling to the underlying FMS (In,Fe)As layer. These findings provide a guideline for material design of epitaxial Al/(In,Fe)As heterostructures, which may serve as a promising platform for investigating proximity-induced superconducting and magnetic phenomena in semiconductor-based hybrid quantum devices.