Three recent studies present different solutions to key problems limiting the use of gallium nitride (GaN) in power electronics and communications: high-voltage endurance, reduced contact resistance, and thermal management. The results come from research teams led by institutions including the École polytechnique fédérale de Lausanne (EPFL), the Massachusetts Institute of Technology (MIT), and Nagoya, Cornell, and Georgia Tech universities and Penn State, in addition to Chinese research institutions.
A transistor that withstands nearly 4 kilovolts
EPFL researchers developed a new class of GaN transistors called intrinsic polarization superjunction (iPSJ). The device, made from GaN layers on a low-cost silicon substrate, withstood a voltage of nearly 4 kilovolts before breakdown while maintaining low resistance, according to the team.
The design relies on the natural polarization effect in GaN to create two parallel arrays of positive charges and electrons. Adjusting the thickness of the layers balances the two charges, preventing excess charge from accumulating when the transistor is turned off and helping distribute the voltage evenly across the device. The approach also eliminates the need for chemical doping. The researchers compare this with conventional GaN transistors, which typically break down at around 600 to 650 volts.
The team believes that voltage endurance across a broad temperature range could make the technology suitable for electric-vehicle systems and industrial power systems, but the presented material does not yet establish that these devices are ready for commercial production.
Reducing p-GaN contact resistance
In another effort, researchers from Nagoya University, MIT, Cornell University, City University of Hong Kong, and the Chinese Academy of Sciences reduced the contact resistance of p-type GaN contacts by depositing an ultrathin layer of magnesium on the p-GaN surface and then heating it at 600 degrees Celsius for five minutes.
The method achieved a specific contact resistance of (1–3) × 10⁻⁴ Ω cm², one of the lowest values reported in research for thin p-GaN contacts, according to the team. Using a thin magnesium layer avoided surface roughness, while the thin samples showed that oxidation was confined to the uppermost surface layer even at a thickness of 10 nanometers.
During the brief thermal treatment, magnesium diffuses into the surface region and narrows the depletion region, enhancing hole tunneling and reducing resistance. The researchers say the process is simpler, faster, and less expensive than bottom-up crystal growth, and they are working to apply it to LEDs and power transistors for electric vehicles.
Diamond as a layer for distributing heat
The third study, from MIT, Georgia Tech, and Penn State, integrated GaN transistors into an ultrathin layer of single-crystal diamond. The layer acts as a thermal spreader that balances temperatures between GaN and silicon, allowing the device to approach peak performance without sacrificing reliability.
The process begins by cutting small GaN pieces from a wafer and then etching cavities into the diamond using a femtosecond laser. After placing a bonding layer inside the cavities and inserting the pieces, heat and pressure are applied, followed by the addition of insulating and metal layers over the structure. The team used the technique to fabricate a 4-watt wireless power amplifier intended for 6G applications in the FR3 band.
Potential applications could extend to high-power radars, satellite communications, industrial drones, and power conversion in data centers. In practice, the results show that improving GaN does not depend on the channel material alone; interconnects, thermal management, and packaging may all determine whether theoretical performance can be used in an actual system.