Demonstration of HfO ₂ -Based Gate Dielectric with Low Interface State Density and Sub-nm EOT on Ge by Incorporating Ti into Interfacial Layer

HfO₂-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 Dit of approximately 2.5 ×,1011 eV - 1 cm - 2, and a smaller Dit increment of approximately 1 × 1011eV-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.