Crystalline SrZrO₃ deposition on Ge (001) by atomic layer deposition for high-k dielectric applications

Heteroepitaxial growth of crystalline SrZrO₃ (SZO) on Ge (001) by atomic layer deposition is reported. Ge (001) surfaces are pretreated with 0.5-monolayers (ML) of Ba and an amorphous ∼3-nm SZO layer is grown from strontium bis(triisopropylcyclopentadienyl), tetrakis (dimethylamido) zirconium, and water at 225 °C. This ∼3-nm layer crystallizes at 590 °C and subsequent SZO growth at 225 °C leads to crystalline films that do not require further annealing. The film properties are investigated using X-ray photoelectron spectroscopy, x-ray diffraction, aberration-corrected electron microscopy, and capacitance-voltage measurements of metal-oxide semiconductor capacitor structures. Capacitance-voltage measurements of the SrZrO₃/Ge heterojunctions reveal a dielectric constant of 30 for SrZrO₃ and a leakage current density of 2.1 × 10⁻⁸A/cm² at 1 MV/cm with an equivalent oxide thickness of 0.8 nm. Oxygen plasma pretreatment of Ge (001), Zintl layer formation with 0.5 ML Ba, and atomic deuterium post-growth treatment were explored to lower interface trap density (D_it) and achieved a D_it of 8.56 × 10¹¹ cm⁻² eV⁻¹.