Investigation of the electrical properties of the alkaline-earth oxides BaO, SrO and Ba0.7Sr0.3O on Si(001) as alternative gate dielectrics

We present first investigations of the electrical characteristics of high-k amorphous BaO, SrO and crystalline Ba0.7Sr0.3O films on n-Si(001). The MOS structures were grown in a UHV chamber on structured SiO2 samples with Si(001) windows and were capped with Au layers afterwards for ex-situ electrical characterization. The smallest capacitance equivalent oxide thicknesses (relative to SiO2) achieved so far in BaO, SrO and Ba0.7Sr0.3O MOS-diodes were 1.0, 3.5 and 1.6 nm at oxide thicknesses of 5, 10 and 10 nm, respectively. The corresponding leakage current densities at + 1 V accumulation bias were 2.1, 1.3 · 10− 5 and 4.7 · 10− 6 A/cm2. The lowest interface trap densities observed at ∼ 0.2 eV below the conduction band in MOS-diodes with BaO, SrO and Ba0.7Sr0.3O films were 5.2 · 1012, 9.7 · 1011 and 9.1 · 1010 eV− 1 cm− 2, respectively. These results suggest that alkaline-earth oxides might be interesting materials for application as high-k gate dielectrics.