Next-generation power chips top 3,400 volts in 5x voltage leap for future EVs

The tiny chargers that power our phones have a secret weapon known as gallium nitride (GaN). This material lets them handle electricity efficiently without needing bulky components. However, ask the same material to handle much higher voltages, and it runs into a problem that has kept GaN from challenging silicon in some of the most demanding power systems. Now, researchers at EPFL have found a way to make GaN handle more than 3.4 kilovolts by turning one of the material’s natural properties into a built-in defense against electrical breakdown. The idea sounds almost counterintuitive. Rather than adding special chemicals to control how electric charge moves through the device, the researchers engineered the GaN layers so they naturally produce matching sheets of positive and negative charge. This prevents electricity from piling up in one vulnerable spot when the transistor switches off, allowing the electric field to spread more evenly. The result is an unusually high-voltage GaN device that could help bring smaller, more efficient power electronics to electric vehicles, renewable-energy systems and energy-hungry AI data centers. Letting GaN balance its own charge Researchers at EPFL’s POWERlab tackled the problem by exploiting something GaN naturally does. Because of spontaneous and piezoelectric polarization in its crystal structure, GaN heterostructures can naturally induce extremely thin sheets of mobile electrons and holes. In conventional GaN electronics, one of these sheets contains mobile electrons, forming a two-dimensional electron gas, or 2DEG. The researchers engineered an additional GaN layer that naturally creates a second sheet containing mobile holes, called a two-dimensional hole gas, or 2DHG. The crucial step was making the two charge sheets nearly equal. By adjusting the thickness of the GaN cap layer, the researchers could tune the amount of positive charge until it closely matched the negative charge carried by the electron sheet. In their devices, the 2DEG contained about 1.03 × 10¹³ electrons per square centimeter, while the 2DHG contained about 1.05 × 10¹³ holes per square centimeter—a difference of less than 2%. This balance prevents the charge pile-up that normally creates a dangerous electric-field spike when the transistor turns off. Instead, the positive and negative charges compensate for each other, allowing the electric field to spread more evenly through the device. “We achieve this by exploiting a natural polarization effect that is unique to GaN. Our work could enable robust, efficient, high-voltage power electronics at much more compact scales,” Elison Matioli, a professor at EPFL and director of POWERlab, said. The approach also removes the need for intentional doping to create the balancing charge. This could be important because doped charge-balancing structures can behave differently as temperatures change. “Doping-based charge balancing in GaN can be highly temperature sensitive. Our doping-free design is key to the robustness of our device,” Yuan Zong, one of the lead researchers and a PhD student at EPFL, said From balanced charges to kilovolts The idea worked in physical devices built from layers of GaN on a relatively inexpensive silicon substrate. The team first demonstrated Schottky barrier diodes with breakdown voltages above 3.9 kV while maintaining a specific on-resistance as low as 4.7 mΩ cm². The charge balance was critical to that result. A control device with mismatched electron and hole concentrations broke down below 1 kV, while the charge-balanced device reached 3.9 kV. The transistor versions sustained 3.5 kV in normally-on operation and 3.4 kV in normally-off operation. That is more than five times the voltage rating of many commercial GaN power devices. The performance also held up under heat. The diodes maintained breakdown voltages above 3.3 kV at temperatures up to 125°C. During repeated high-voltage operation, their dynamic on-resistance increased by less than 15% at up to 3 kV. The transistor’s dynamic on-resistance was separately tested only up to 650 V, however, the researchers’ measurement setup introduced parasitic effects at higher switching voltages. This combination matters because a transistor that survives high voltage but wastes large amounts of energy through resistance would still be of limited use. The new design aims to address both problems at once. “Our device can hold high voltage across a wide temperature range, making it suitable for EVs or industrial power systems, where electronics must operate reliably under high temperatures and electrical stress,” Luca Mazzone, first author of the study, said. A bigger role for GaN The advance could eventually benefit electric vehicles, renewable-energy systems and the power infrastructure used by energy-hungry AI data centers, where smaller and more efficient power converters could reduce both hardware size and heat losses. However, the devices are still laboratory demonstrations, and their substrate imposes a limit. The GaN-on-silicon structure used by the team restricted the maximum breakdown voltage, meaning different substrates could potentially allow the devices to go even higher. The researchers are also looking beyond voltage alone. In complementary work, the POWERlab developed multi-channel GaN devices that spread current across several conduction paths, lowering resistance and reducing overheating. The next step “is to combine these two approaches to address the twin challenges facing next-generation power electronics: handling very high voltages safely, while minimizing electrical resistance and the resulting energy loss,” Matioli said. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Rupendra Brahambhatt is an experienced writer, researcher, journalist, and filmmaker. With a B.Sc (Hons.) in Science and PGJMC in Mass Communications, he has been actively working with some of the most innovative brands, news agencies, digital magazines, documentary filmmakers, and nonprofits from different parts of the globe. As an author, he works with a vision to bring forward the right information and encourage a constructive mindset among the masses.