Electronic structure and band offsets of high-dielectric-constant gate oxides

The decrease of the dimensions of metal oxide semiconductor (MOS) transistors has led to the need for alternative, high-dielectric-constant (κ) oxides to replace silicon dioxide as their gate dielectric [1–3]. Silicon dioxide layers thinner than 1.6–2 nm have a leakage current over 1 A cm⁻² due to direct tunnelling through the oxide [4], which is too large for portable devices. As tunnelling decreases exponentially with thickness, the tunnelling current can be reduced by using thicker layers of high-κ oxides, which have the same equivalent capacitance or equivalent silicon dioxide thickness ‘EOT’.