Our mobile phones today handle far more wireless signals and services than earlier generations. The same is true of the sophisticated equipment behind mobile networks, such as base stations, and emerging technologies such as self-driving cars. Inside these systems, radio-frequency switches act like traffic controls, allowing signals to pass or blocking them as needed. The signal-sending and receiving unit in a 2G system used about four such switches, while 5G and future 6G systems may require 50 to more than 100. Fitting so many switches onto a chip can increase the size, cost and power use of wireless hardware.
An international team led by Associate Professor Mario Lanza from the Department of Materials Science and Engineering at the College of Design and Engineering, National University of Singapore (NUS CDE), has developed compact switches that retain their settings without continuous power. The study marks the first use of this type of device, known as a memristive radio-frequency switch, to reconfigure working monolithic microwave integrated circuits (MMICs) — chips that combine several high-frequency signal-handling functions.
Made from hexagonal boron nitride (hBN) and integrated directly onto gallium nitride (GaN) microchips, the switches adjusted signal strength, redirected signals and changed the frequencies selected by a filter. Their small footprint leaves more chip space for other radio functions, while their ability to retain a setting reduces the power needed to maintain a device's configuration.
The approach could help technologies such as phones, mobile networks and self-driving cars support more wireless functions without requiring larger or more power-hungry radio hardware. The team's findings were published in Nature on 8 July 2026.
How the switch remembers
Most radio-frequency switches in commercial chips use transistors or diodes. Though reliable, they occupy chip space and typically need continuous power to hold their state. A memristive switch works differently: its electrical resistance can be changed and retained, allowing it to pass, block or reduce a signal.
The researchers constructed each switch by placing a layer of hBN about eight nanometres thick between two gold electrodes. A brief electrical pulse creates or breaks a nanoscale gold pathway through the hBN, setting the switch's resistance. The resulting electrical state remains after the pulse ends — in effect, the switch remembers its last instruction.
Each hBN switching element measured only 2 by 2 micrometres. By contrast, the conventional switches cited in the paper occupy at least 0.1 square millimetres — around 25,000 times as much space on a chip. This smaller footprint could help chip designers accommodate the growing number of switches required by 5G and future 6G systems without a corresponding increase in chip size.
Making the switches smaller was only part of the challenge, as the researchers also had to work with the chip's existing control electronics. They built the hBN switches on the upper wiring layers of commercially manufactured GaN chips, leaving the underlying transistor circuitry intact. They then connected the switches to GaN transistors already on the chip. These transistors acted as drivers, supplying and limiting the current needed to change each switch's setting. This approach shows that hBN switches can be added to an established chip platform without redesigning its underlying transistor layer.
"Earlier studies showed that individual hBN devices could handle high-frequency signals. The unanswered question was whether the switches and their control electronics could work together inside useful circuits," said Assoc Prof Lanza. "Our work shows that they can function as part of a complete GaN chip."
Putting the switches to work
The switches operated at frequencies up to 100 gigahertz, covering bands used by 5G and being explored for 6G. The best series switch recorded a signal loss of 0.3 decibels, meaning that about 93% of the signal power passed through. For comparison, across devices tested at 49 gigahertz, the median loss was 1 decibel. Overall performance approached that of commercial alternatives based on phase-changing materials and exceeded previously reported transistor-based switches on GaN and comparable semiconductor platforms.
"The devices retained their conducting state after two weeks of storage and 24 hours of heating at 175 degrees Celsius, which is 50 degrees Celsius above the temperature at which earlier studies report retention issues in phase-change switches," said Dr Sebastian Pazos, a senior device engineer working with Assoc Prof Lanza and first author of the paper.
The best switch-and-driver pair completed 3,250 switching cycles, compared with 2,000 in the team's earlier standalone hBN devices, and 30 in a separate study of similar switches. However, the researchers noted that this does not yet demonstrate commercial reliability, as several devices failed after tens to hundreds of cycles when their thin electrodes became damaged. More development is therefore needed to achieve commercial reliability.
The team incorporated the switches into three working circuits: an attenuator adjusted signal strength; a power divider selected a signal route; and a filter shifted the frequencies it allowed through by 6 gigahertz. These results demonstrated that the switches could control complete circuit functions, rather than operate only as laboratory devices.
A step towards commercial readiness
The team noted that two engineering challenges remain. Transferring hBN onto a completed chip adds manufacturing complexity, while the switches must withstand many more operating cycles before commercial viability can be achieved.
Follow-up research is underway to prioritise transfer-free integration by producing layered hBN directly on GaN at temperatures compatible with microchip manufacturing. In addition, the researchers propose using thicker electrodes and smoother, planarised GaN surfaces to improve durability. The team also recommended using computer models to help researchers design larger circuits and predict their performance before fabrication.
