Electrical Properties of Single Crystalline CeO₂ High-k Gate Dielectrics Directly Grown on Si (111)

We have grown epitaxial single crystalline CeO₂ directly on Si (111) by molecular beam epitaxy. Metal-insulator-semiconductor (MIS) capacitors were fabricated to evaluate electrical properties of CeO₂ films. By eliminating an interfacial layer, equivalent oxide thickness (EOT) as small as 0.38 nm was obtained for a CeO₂ physical thickness of 5 nm. The dielectric constant (ε) was calculated to be ε∼52, which is two times larger than the value reported for bulk (polycrystalline) CeO₂ (ε∼26). Enhancement of ε is probably attributable to the anisotropy of the single crystalline CeO₂ and/or the lattice distortion of CeO₂ directly grown on Si. A leakage current density of ∼ 1 A/cm² was obtained at an equivalent electrical field of 5 MV/cm for the CeO₂ MIS capacitors, which is much smaller than the expected value for SiO₂ capacitors with the same EOT. It is revealed that single crystalline CeO₂ is promising as an alternative gate dielectric.