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

We demonstrate voltage-triggered self-sustained relaxation oscillation (SSRO) in two-terminal devices based on highly oriented vanadium dioxide (VO₂) grown on silicon substrates with aluminum nitride (AlN) buffer layers. Cross-sectional TEM and XRD confirm high-quality VO₂/AlN/Si heteroepitaxy, while SEM reveals uniform morphology. The films exhibit sharp insulator-to-metal transitions with resistance changes of > 10⁴ and electrical resistivities of ∼1.49 × 10^-1 and ∼1.31 × 10^-5 Ω·m at 300 and 390 K, respectively. Statistical analysis of 100 devices shows consistent switching voltages near 6.3 V, demonstrating reproducibility. The AlN buffer enables lattice-matched growth, acts as a diffusion barrier, and induces tensile strain, increasing the transition temperature (T_c ≅ 350 K) and broadening the operational window. Voltage oscillations measured across 2-10 kΩ resistors show frequency modulation, while temperature-dependent and time-resolved tests confirm robust stability. In a simple series circuit with a 6 kΩ resistor, the oscillation frequency can be controlled by voltage from ∼296 to ∼1076 kHz, with a tuning sensitivity of ∼260 kHz/V. This frequency tuning range can be extended using external capacitors. These VO₂/AlN/Si heterostructures provide a compact, CMOS-compatible, low-power platform for oscillatory devices, offering large resistance modulation, thermal robustness, and reproducible performance for neuromorphic circuits and spiking networks.