  Hybrid semiconductor-ferromagnetic insulator heterostructures are interesting
due to their tunable electronic transport, self-sustained stray field and local
proximitized magnetic exchange. In this work, we present lattice matched hybrid
epitaxy of semiconductor - ferromagnetic insulator InAs/EuS heterostructures
and analyze the atomic-scale structure as well as their electronic and magnetic
characteristics. The Fermi level at the InAs/EuS interface is found to be close
to the InAs conduction band and in the bandgap of EuS, thus preserving the
semiconducting properties. Both neutron and X-ray reflectivity measurements
show that the ferromagnetic component is mainly localized in the EuS thin film
with a suppression of the Eu moment in the EuS layer nearest the InAs. Induced
moments in the adjacent InAs layers were not detected although our ab initio
calculations indicate a small exchange field in the InAs layer. This work
presents a step towards realizing high quality semiconductor - ferromagnetic
insulator hybrids, which is a critical requirement for development of various
quantum and spintronic applications without external magnetic fields.
