Reconfigurable Radio-Frequency Microchips Enabled by Two-Dimensional Memristive Switches
The relentless scaling of wireless communication toward millimeter-wave (mmWave) and sixth-generation (6G) systems has exposed fundamental limitations in conventional radio-frequency (RF) switches based on field-effect transistors, p-i-n diodes, and microelectromechanical systems, which suffer from trade-offs among insertion loss, isolation, footprint, power consumption, actuation voltage, and integration complexity. Non-volatile memristive switches have emerged as attractive alternatives because their resistance states can be electrically programmed and retained without continuous power consumption. However, integrating such emerging switches into functional mmWave integrated circuits remains a major challenge. Pazos et al. reported a major step by co-integrating two-dimensional hexagonal boron nitride (hBN) memristive RF switches with a commercial gallium nitride (GaN) high-electron-mobility transistor (HEMT) monolithic microwave integrated circuit (MMIC) platform. Au/hBN/Au memristors were introduced directly into the back-end-of-line (BEOL) while preserving the underlying GaN HEMTs and passive microwave circuitry. The active switching area is approximately 2 μm × 2 μm. The devices exhibited a pristine capacitance of approximately 24.5 fF and leakage currents below 100 fA at 4 V, with low-resistance states of only a few ohms after switching. Cross-sectional transmission electron microscopy revealed a well-defined ~8-nm layered hBN structure before electrical stressing, and a filament-like pathway accompanied by Au penetration after switching to the low-resistance state. The work demonstrates competitive wideband switching performance, high-temperature non-volatility, transistor-assisted programming, continuous RF attenuation, selective signal routing, and frequency-reconfigurable resonators, establishing a new integration paradigm for programmable mmWave electronics.