Broadly Tunable Self-Sustained Oscillations in CMOS-Compatible VO₂/AlN/Si Devices

Area of Science:

• Materials Science
• Solid State Physics
• Device Physics

Background:

• Vanadium dioxide (VO2) exhibits a phase transition crucial for electronic devices.
• Achieving high-quality VO2 films on silicon is challenging due to lattice mismatch and diffusion.

Purpose of the Study:

• To demonstrate voltage-triggered self-sustained relaxation oscillations (SSRO) in VO2-based devices.
• To investigate the role of aluminum nitride (AlN) buffer layers in VO2/Si heterostructures.
• To explore the potential of these heterostructures for neuromorphic circuits.

Main Methods:

• Epitaxial growth of VO2 films on AlN/Si substrates using techniques like TEM and XRD.
• Fabrication and characterization of two-terminal devices.
• Electrical measurements including I-V characteristics, resistance temperature dependence, and oscillation frequency modulation.
• Statistical analysis of device performance.

Main Results:

• High-quality VO2/AlN/Si heteroepitaxy with uniform morphology.
• Sharp insulator-to-metal transitions in VO2 films with large resistance changes (>10^4).
• Reproducible voltage-triggered SSRO with consistent switching voltages (~6.3 V).
• AlN buffer layer enhances lattice matching, acts as a diffusion barrier, and induces strain, optimizing the transition temperature (~350 K).
• Voltage-controlled frequency modulation of oscillations from ~296 to ~1076 kHz with a tuning sensitivity of ~260 kHz/V.

Conclusions:

• VO2/AlN/Si heterostructures provide a stable, reproducible platform for oscillatory devices.
• The AlN buffer layer is critical for enabling high-performance VO2 devices on silicon.
• These devices are CMOS-compatible and suitable for low-power applications in neuromorphic computing and spiking networks.