Temperature-Dependent Admittance Analysis of HfO2 Gate Dielectrics on Nitrogen- and Sulfur-Passivated Ge

In this work, we characterize MOS capacitors with HfO
₂
gate dielectrics that utilize sulfur (S) passivation formed by pre-treatment of the Ge surface in an aqueous (NH
₄
)
₂
S solution before HfO
₂
deposition, and compare the results with those using the more-standard N-passivation. Using temperature-dependent admittance measurements, we find that the S-passivated samples have lower minimum D
_it
and reduced flat-band shift, but also display larger accumulation dispersion and hysteresis than N-passivated samples. Results of admittance spectroscopy analysis also suggest that the energy distributions of the interface states are fundamentally different in the two sample types