(Invited) Tuning Dielectric Properties of Epitaxial Lanthanide Oxides on Silicon

Abstract

The dielectric properties of thin crystalline oxides grown on silicon are sensitive to small variations in structure and symmetry. Here, we report about different investigations on strain-induced effects on dielectric properties. First, we report on the dependence of the dielectric constant on layer thickness for epitaxial Gd2O3 on Si(111). The K-value strongly decreases with increasing layer thickness and reaches the bulk value at around 8 nm. Controlling the oxide composition in ternary (Gd1-xNdx)2O3 thin films enables us to tune the lattice mismatch to silicon, and thus the strain-induced variation in the dielectric constants. We show that solely tetragonal distortion of the cubic lattice is not sufficient to explain the huge enhancement in K-values; more severe strain induced structural phase deformations take place. Further, dielectric properties of epitaxial oxide thin films have been found to improve significantly by incorporation of suitable dopants. We observe substantial reduction of the leakage current density in nitrogen-doped Gd2O3 layers indicating that nitrogen doping can be an effective route to eliminate the adverse effects of the oxygen vacancy induced defects in the oxide layers.