We demonstrate the benefit of using a low work-function metal (Yb) to lower the barrier height and hence, the contact resistivity (ρc) in unpinned metal-interfacial layer-semiconductor (MIS) contacts on n-type Ge and Si. Metal/doped TiO2−x/n-Ge and n-Si MIS diodes fabricated with varying TiO2−x thickness (1–5 nm) exhibit higher (upto 100X) current densities and lower contact barrier heights (upto 30%) for Yb versus Ti metallization. A combination of low work-function Yb, doped TiO2−x with low conduction band offsets w.r.t Si and Ge, and high substrate doping( n+-Si:2×1020 cm−3 and n+-Ge:2.5×1019 cm−3) is shown to result in ultra-low ρc values of 2.1×10−8 Ω.cm2 (Si) and 1.4×10−8 Ω.cm2 (Ge) for Yb/TiO2−x contacts, significantly lower than Ti/TiO2−x control devices, and the best reported contact resistivity on n-Ge till date.