Very large remanent polarization in ferroelectric Hf_1-xZr_xO₂ grown on Ge substrates by plasma assisted atomic oxygen deposition

Plasma assisted atomic oxygen deposition was used to grow polycrystalline ferroelectric Hf_1-xZr_xO₂ (x = 0.5–0.7) on technologically important (100) Germanium substrates showing sharp crystalline interfaces free of interfacial amorphous layers and strong evidence for the presence of a predominately orthorhombic phase. The electrical properties, evaluated using metal-ferroelectric-semiconductor (MFS) capacitors, show symmetric and robust ferroelectric hysteresis with weak or no wake-up effects. The MFS capacitors with x = 0.58 show very large remanent polarization up to 34.4 μC/cm² or 30.6 μC/cm² after correction for leakage and parasitics, combined with good endurance reaching 10⁵ cycles at a cycling field of 2.3 MV/cm. The results show good prospects for the fabrication of Ge ferroelectric field effect transistors (FeFETs) for use in 1 T FeFET embedded nonvolatile memory cells with improved endurance.