Structural and electrical characteristics of metal-insulator-semiconductor diodes based on Y2O3 dielectric thin films on silicon

Metal-insulator-semiconductor (MIS) diodes with an electron-beam-deposited and oxygen-annealed thin (≊80 nm) Y2O3 dielectric layer on p-Si(100) show metal-oxide-semiconductor capacitor action. As-deposited Y2O3 films are oxygen-deficient amorphous and show low 5×10−9 A leakage currents for a capacitor area of 0.785 mm2 and breakdown fields of 1.0 MV/cm. Amorphous Y2O3 film crystallizes to a bcc phase by annealing at 400 °C causing increased conduction due to asperities related localized high-field regions at contacts while its dielectric constant increases from a low value of 9.0ε0 to 27ε0. Annealing the Y2O3 film on Si above the crystallization temperature in the range 425 °C<Ts < 650 °C leads to growth of an about 5-nm-thick intermediate SiO2 layer at the Y2O3/SiO2 interface. A remarkable two orders of magnitude decrease in leakage current to 2×10−11 A and increase in breakdown field to 2.0 MV/cm is observed for MIS diodes with composite Y2O3/SiO2 dielectric. Current-voltage behavior in the inversion mode demonstrates existence of positive charge trapping states at the Y2O3/SiO2 interface region. The current transport in Y2O3 and Y2O3/SiO2 insulator layers is dominated by bulk conduction behavior of Y2O3 through the Poole–Frenkel mechanism.