High-κ Dielectric (HfO₂)/2D Semiconductor (HfSe₂) Gate Stack for Low-Power Steep-Switching Computing Devices.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Advanced gate stacks are crucial for next-generation semiconductor devices.
• Two-dimensional (2D) materials offer unique electronic properties but require high-quality interfaces.
• Hafnium-based materials are promising for high-κ dielectrics.

Purpose of the Study:

• To fabricate and characterize a high-quality HfO2/HfSe2 gate stack.
• To investigate the interface properties and dielectric performance.
• To demonstrate steep-switching transistor characteristics for post-silicon electronics.

Main Methods:

• Plasma oxidation for HfO2 gate dielectric formation on 2D HfSe2.
• Density Functional Theory (DFT) calculations for interface mechanism analysis.
• Fabrication and characterization of field-effect transistors (FETs) and impact ionization FETs.

Main Results:

• Achieved an atomically sharp HfO2/HfSe2 interface with low interface trap density (Dit ≈ 5 × 10^10 cm^-2 eV^-1).
• HfO2 exhibited a high dielectric constant (κ ≈ 23) and low leakage current (≈10^-3 A cm^-2) at an equivalent oxide thickness of ≈0.5 nm.
• Demonstrated FETs with ideal subthreshold slope (SS ≈ 61 mV dec^-1) and high Ion/Ioff ratio (≈10^8).
• Fabricated impact ionization FETs exhibiting steep-switching characteristics (SS = 3.43 mV dec^-1), surpassing the Boltzmann limit.

Conclusions:

• Plasma oxidation enables high-quality HfO2/HfSe2 gate stacks with superior interface properties.
• The developed gate stack is suitable for advanced transistor applications, including steep-switching devices.
• This work represents a significant advancement towards post-silicon, energy-efficient computing electronics.