Researchers have shown that a single radio chip can be reconfigured to do different jobs, by building switches only a few atoms thick into the wiring of gallium nitride (GaN) chips. The work, reported in Nature and documented in an openly shared data repository, comes from an international collaboration whose contact researchers are Sebastian Matias Pazos and Mario Lanza, with colleagues at the National University of Singapore, King Abdullah University of Science and Technology (KAUST), the Tyndall National Institute, University College Cork, Carnegie Mellon University and the National Technological University.
The circuits that carry most high-frequency wireless traffic - monolithic microwave integrated circuits, or MMICs - are usually fixed to a single purpose. Adding the switches that would let them be reprogrammed has been expensive, hungry for chip area and a drag on performance, which has kept genuinely flexible radio hardware out of reach.
The team's answer is a memristive switch, whose electrical resistance can be set and then held in memory. It is made from two-dimensional hexagonal boron nitride (hBN), a layered material only atoms thick, and is fabricated directly on the chip's back-end-of-line - the upper interconnect layers - rather than added as a separate part. Because the switch keeps its on or off state without a constant supply of power, it points toward more energy-frugal designs.
In testing, the wideband switches operated at frequencies up to 100 GHz, well into the millimetre-wave range set aside for 6G. They gave up as little as 0.3 dB of signal when open and blocked it by more than 15 dB when closed. A programmed state lasted two weeks, and the on-state resistance stayed stable at 175 degrees Celsius. Driven through a one-transistor, one-memristor cell, the switches withstood 3,250 switching cycles, an advance for radio switches built from two-dimensional materials.
From single switch to working circuits
What distinguishes the study is that the switches were not only measured on their own but assembled into functioning circuits. On the GaN platform the researchers built configurable attenuators, power dividers and programmable resonators - components that can be tuned or repurposed after a chip has been made. According to the authors, it is the first time such memristive switches have been realised inside MMIC circuits.
The result is a laboratory demonstration, not yet a product. But by pairing an atom-thin, non-volatile material with the rugged, high-power GaN technology already common in wireless base stations, it maps a practical path toward radio chips that can be reprogrammed instead of replaced - a helpful ingredient for the more capable and more efficient networks now on the drawing board.