Gd₂O₃, 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 Si_0.74Ge_0.26 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× 10^10cm-2 and 4.8× 10¹¹eV^-1cm^-2, respectively, which are the lowest among all the oxide films of the present study.