A fluorite-structured HfO₂/ZrO₂/HfO₂ superlattice based self-rectifying ferroelectric tunnel junction synapse

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectric tunnel junctions (FTJs) are crucial for next-generation electronic devices.
• Enhancing FTJ performance, particularly on/off ratio and rectification, is a key research area.
• Developing materials for neuromorphic computing requires high-performance, reliable memory elements.

Purpose of the Study:

• To propose and investigate a self-rectifying ferroelectric tunnel junction (FTJ) utilizing a HfO2/ZrO2/HfO2 superlattice (HZH SL).
• To enhance the remnant polarization (Pr) and modulate the energy barrier for improved device performance.
• To explore the potential of this FTJ for neuromorphic computing applications, specifically artificial synapses.

Main Methods:

• Fabrication of a 6 nm-thick HZH SL integrated with Al2O3 and TiO2 layers.
• Characterization of the ferroelectric properties, including remnant polarization (Pr).
• Analysis of conduction mechanisms (thermal injection vs. Fowler-Nordheim tunneling) and Schottky barrier formation.
• Device performance evaluation, including on/off ratio and rectifying ratio.
• Simulations for array integration potential and neuromorphic computing applications.
• Experimental validation in a 9x9 crossbar array.

Main Results:

• The HZH SL effectively suppressed non-ferroelectric phases and increased Pr.
• Achieved a large on/off ratio of 1273 by switching conduction mechanisms.
• Demonstrated a self-rectifying property with a rectifying ratio of 1550 due to asymmetric Schottky barriers.
• Simulations indicated potential for integrated arrays (>7k) with a 10% read margin.
• Attained >92% image recognition accuracy for artificial synapse applications.
• Confirmed self-rectifying behavior and reliability in a 9x9 crossbar array.

Conclusions:

• The proposed HZH SL-based FTJ offers a promising pathway for high-performance electronic devices.
• The device exhibits excellent self-rectifying characteristics and a significant on/off ratio.
• This technology holds substantial potential for advancing neuromorphic computing and artificial synapse development.
• The demonstrated reliability in a crossbar array suggests scalability and practical applicability.