The POWERlab's intrinsic polarization superjunction (iPSJ). Credit: 2026 Alain Herzog/EPFL CC BY SA 4.0
Inside every electronic device, the flow of electricity is controlled by a switch called a transistor. For decades, these switches were made from silicon. More recently, engineers have turned to a material called gallium nitride (GaN), which enables small, efficient devices like smartphone chargers.
However, at very high voltages, electric fields inside these transistors can concentrate at specific points, causing them to fail prematurely. As a result, today's GaN devices still struggle to perform at the highest voltage levels achieved by silicon.
To overcome this limitation, researchers in the Power and Wide-band-gap Electronics Research Lab (POWERlab) in EPFL's School of Engineering have introduced a new class of GaN transistor: the intrinsic polarization superjunction, or iPSJ.
The chip-sized device, made from layers of gallium nitride on a low-cost silicon base, can withstand nearly 4 kilovolts (kV) before breaking down, a record for this type of technology. At the same time, it maintains low resistance, helping to reduce energy losses that would otherwise be released as heat.
