Scientists have built a new type of high-frequency microchip that can be reprogrammed after manufacturing, by combining gallium nitride (GaN) circuitry with switches made from an ultra-thin layered material called hexagonal boron nitride (hBN), according to a study published in Nature.
The work addresses a long-standing bottleneck in monolithic microwave integrated circuits, or MMICs, a technology expected to play a major role in telecommunications as networks push toward 5G and beyond. These circuits rely on specialized semiconductors tuned for particular performance needs, but fitting high-frequency switches onto them has been costly and space-intensive, limiting how these chips can be built and used.
Memristive radio-frequency switches — devices that retain a resistance state and are relatively simple to fabricate — have been seen as a promising alternative because of their strong performance at the device level. However, according to the study, they had never before been successfully built into a working MMIC circuit.
Switches built into the chip's wiring layer
The research team fabricated wideband switches directly into the back-end-of-line wiring of GaN chips, using multilayer hBN as the active switching material. These switches operated at frequencies up to 100 GHz, with insertion losses as low as 0.3 decibels and isolation better than 15 decibels — both markers of how efficiently a switch passes or blocks a signal.
The devices also proved durable under demanding conditions. They retained their programmed state for two weeks, kept a stable on-state resistance at 175 degrees Celsius, and showed linear power handling within 0.28 decibels when tested up to 18 dBm. The switches had an extrapolated 1-dB compression point — a measure of how much power a device can handle before its performance starts to degrade — with a mean value of 30.52 dBm.
To drive the switches, the team used a one-transistor, one-memristor cell design, which achieved 3,250 cycles of endurance. The study describes this as an improvement for memristive radio-frequency switches based on two-dimensional materials.
Using this platform, the researchers demonstrated several reconfigurable components on a single GaN chip: memristive-configurable attenuators, power dividers, and programmable resonators, all controlled through the embedded hBN switches.
The advance points toward microwave hardware that can be adjusted electronically for different tasks rather than requiring separate, fixed-function chips — a capability the study's authors say has been difficult to achieve with existing switch technologies integrated into MMIC platforms.
The dataset underlying the study's conclusions has been made publicly available via Zenodo, with additional supporting data available from the study's corresponding authors upon request.