A unified model for insulator selection to form ultra-low resistivity metal-insulator-semiconductor contacts to n-Si, n-Ge, and n-InGaAs

A comprehensive, physics-based unified model is developed for study of low resistivity metal-insulator-semiconductor (M-I-S) ohmic contact. Reduction in metal-induced gap state density and Fermi unpinning in semiconductor as a function of insulator thickness is coupled with electron transport including tunnel resistance through the metal-insulator-semiconductor (M-I-S) system to calculate specific contact resistivity at each insulator thickness for n-Si, n-Ge, and n-InGaAs. Low conduction band offset results in ∼1×10−9 Ω−cm2 contact resistivity with TiO2 insulator on n-Si, ∼7×10−9 Ω−cm2 can be achieved using TiO2 and ZnO on n-Ge, and ∼6×10−9 Ω−cm2 can be achieved with CdO insulator on n-InGaAs, which meet the sub-22nm CMOS requirements.