Gd 2 O 3 , Ga2O3(Gd2O3), Y2O3, and Ga2O3, as high-k gate dielectrics on SiGe: A comparative study

Abstract

We report a comparative study of the electrical properties of some oxides e.g., Gd2O3, Ga2O3(Gd2O3), Y2O3, and Ga2O3 as gate dielectric for strained Si0.74Ge0.26 metal–oxide–semiconductor devices. Secondary ion mass spectroscopy spectra of the Ga2O3(Gd2O3)/SiGe sample showed a significant amount of GaO and GdO along with Ga and Gd signals. The depth profile taken for O, Si, SiO, Ga, Ge, Gd, and GdO showed sharp interface at about 20 nm. Though Gd2O3 and Y2O3 showed the highest resistivity and breakdown strength, Ga2O3(Gd2O3) was found to be most effective for surface passivation of SiGe giving lowest interface state density while pure Ga2O3 was incapable of passivating the SiGe surface. The positive fixed oxide charge and interface state density for Ga2O3(Gd2O3) film were found to be 8.4×1010 cm−2 and 4.8×1011 eV−1 cm−2, respectively, which are the lowest among all the oxide films of the present study.