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.