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

Abstract

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.