Demonstration of HfO2-Based Gate Dielectric With Low Interface State Density and Sub-nm EOT on Ge by Incorporating Ti Into Interfacial Layer

HfO
₂
-based gate stacks with titanium (Ti) incorporated into a GeO
_x
interfacial layer (IL) were fabricated on p-Ge substrates. X-ray photoelectron spectroscopy results, incorporating Ti, can efficiently suppress the GeO volatilization. This contributed to achievement of an equivalent oxide thickness of approximately 0.8 nm, a low interface states density D
_it
of approximately 2.5 × 10
¹¹
eV
^-1
cm
^-2
, and a smaller D
_it
increment of approximately 1 × 10
¹¹
eV
^-1
cm
^-2
after constant negative voltage stress at a field of 8 MV/cm. Therefore, Ti is appropriate for improving the quality of GeO
_x
through high temperature annealing.