Characteristics of ultrathin lanthanum oxide films on germanium substrate: Comparison with those on silicon substrate

Ultrathin La₂O₃ films deposited on Ge substrates were characterized. The films were deposited by electron-beam evaporation in an ultrahigh vacuum system and were subjected to post-deposition annealing at various temperatures in N₂ ambient. There was little interfacial layer growth at the interface of La₂O₃/Ge, which was confirmed by transmission electron microscopy and spectroscopic ellipsometry. Electrical measurements revealed that a small capacitance equivalent thickness of 1.48 nm with a leakage current density of 6 × 10^-7 A/cm ² at 1 V was achieved using a Pt/La₂O₃/Ge structure by post-deposition annealing at 600°C. This result suggests that ultrathin La₂O₃ films can be grown on a Ge substrate by annealing at a sufficiently high temperature for activating the source and drain regions for a Ge metal-oxide-semiconductor field-effect transistor.