Aggressive Equivalent Oxide Thickness of ~0.7 nm on Si_0.8Ge_0.2 Through HfO₂ Dielectric Direct Deposition

This study demonstrated the ultralow equivalent oxide thickness (EOT) value of 0.72 nm and the high-quality high- $\kappa $ /Si0.8Ge0.2 interface on p-type Si0.8Ge0.2 with direct deposition of HfO2. The ultrathin interfacial layer (IL) thickness of ~0.4 nm was observed in the high-resolution transmission electron microscope (HRTEM) images. The high-quality interface might result from the high- $\kappa $ /Si0.8Ge0.2 interface mainly consisting of the higher Si oxidation states, verified by X-ray photoelectron spectroscopy (XPS). Thus, this study refutes the necessity of IL formation and paves the way for low-EOT Si0.8Ge0.2 devices.