Yttrium scandate thin film as alternative high-permittivity dielectric for germanium gate stack formation

We investigated yttrium scandate (YScO₃) as an alternative high-permittivity (k) dielectric thin film for Ge gate stack formation. Significant enhancement of k-value is reported in YScO₃ comparing to both of its binary compounds, Y₂O₃ and Sc₂O₃, without any cost of interface properties. It suggests a feasible approach to a design of promising high-k dielectrics for Ge gate stack, namely, the formation of high-k ternary oxide out of two medium-k binary oxides. Aggressive scaling of equivalent oxide thickness (EOT) with promising interface properties is presented by using YScO₃ as high-k dielectric and yttrium-doped GeO₂ (Y-GeO₂) as interfacial layer, for a demonstration of high-k gate stack on Ge. In addition, we demonstrate Ge n-MOSFET performance showing the peak electron mobility over 1000 cm²/V s in sub-nm EOT region by YScO₃/Y-GeO₂/Ge gate stack