Metal-Induced Trap States: The Roles of Interface and Border Traps in HfO₂/InGaAs

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• High-k dielectrics like Hafnium oxide (HfO2) are essential for advanced semiconductor devices.
• Understanding defects at the dielectric/semiconductor interface is critical for device performance and reliability.
• InGaAs-based devices offer superior electron mobility but face challenges with interface quality.

Purpose of the Study:

• To investigate the influence of different gate metal work functions on defect generation in bulk HfO2 and at HfO2/InGaAs interfaces.
• To identify gate metals that minimize interface and border traps for improved InGaAs device characteristics.
• To establish a systematic approach for selecting optimal gate metals for InGaAs-based high-k devices.

Main Methods:

• Capacitance-voltage (C-V) measurements were employed to characterize device electrical properties.
• Technology Computer-Aided Design (TCAD) simulations were utilized to model device behavior and defect impacts.
• X-ray photoelectron spectroscopy (XPS) was used for surface and interface analysis.
• The Heiman function was applied to analyze border trap density and lifetimes.

Main Results:

• Titanium (Ti) gate metal resulted in the highest density of interface and border traps due to oxidation at the Ti/HfO2 interface.
• Molybdenum (Mo) gate metal formed a stable interface, yielding the lowest observed density of traps.
• Record low values for acceptor-like (1.27 × 10^11 eV⁻¹cm⁻²) and donor-like (3.81 × 10^11 eV⁻¹cm⁻²) interface trap densities (Dit) were achieved.
• Border trap density and lifetimes significantly influence the hysteresis in C-V curves.

Conclusions:

• The work function of the gate metal critically impacts defect formation in HfO2/InGaAs structures.
• Molybdenum (Mo) is identified as a promising gate metal for achieving superior interface quality in InGaAs devices.
• These findings provide essential guidance for the selection of gate metals to optimize InGaAs-based semiconductor devices.