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High-voltage GaN Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) debuted a new class of gallium nitride (GaN) transistor, called an intrinsic polarization superjunction (iPSJ), that can handle very high voltage with minimal energy loss. Made from layers of GaN on a low-cost silicon base, the iPSJ can withstand nearly 4 kilovolts (kV) before breaking down, which the team claims is a record for this type of technology, while maintaining low resistance. “We achieve this by exploiting a natural polarization effect that is unique to GaN,” said Elison Matioli, head of the Power and Wide-band-gap Electronics Research Lab (POWERlab) in EPFL’s School of Engineering, in a press release. “Our next goal 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.” The transistor’s GaN layers are engineered to avoid the charge imbalance that occurs in conventional GaN transistors, which break down at around 600–650 V, by forming a sheet of positive charge alongside the electron sheet. The material thickness was tuned to ensure that the two charge sheets balance each other throughout the device, so when the device turns off, excess charge does not accumulate, allowing the voltage to spread out evenly along the transistor’s length. The approach also eliminates the need for chemical doping. Luca Mazzone, a PhD student at EPFL, highlighted key applications for the technology in a statement: “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.”  [1] Lower resistance p-GaN Researchers from Nagoya University, Massachusetts Institute of Technology (MIT), Cornell University, City University of Hong Kong, and Chinese Academy of Sciences lowered the resistance of p-type gallium nitride (GaN) contacts by depositing an ultrathin magnesium layer onto the p-GaN surface and heating it at 600°C for five minutes. The process achieved a contact resistivity of (1–3) × 10⁻⁴ Ω cm² without damaging the surface, which the team claims is among the lowest reported contact resistivities for thin p-type GaN. Initially, the researchers tried a relatively thick layer (dozens of nanometers) of magnesium, but found that the surface after annealing was too rough. However, using a thinner layer of magnesium presents another issue: it oxidizes easily in air. A protective cap is typically used to isolate it from air, but can add unwanted impurities. The team tried a capless sample as a reference, and surprisingly found that the cap didn’t make a difference, with only the very top layer becoming oxidized even at 10nm thicknesses. During a soft annealing process with lower temperature and shorter time, the ultrathin magnesium layer is rapidly consumed as it diffuses into the surface region of the p-type GaN, leaving a smoother surface. The ultrathin, ultrahigh-concentration magnesium-doped layer narrowed down the contact depletion region and promoted tunneling of holes across it, lowering contact resistance. The process was also simpler, quicker, and cheaper to implement than bottom-up crystal growth, and can be applied after device processing. The team is now working to apply the method to LEDs and power transistors for EVs. [2] GaN embedded in diamond interposer Researchers from the Massachusetts Institute of Technology (MIT), Georgia Tech, and Penn State University embedded gallium nitride (GaN) transistors into an ultrathin layer of diamond, which acts as a heat spreader that normalizes the temperature and allows the transistors to approach peak performance without reducing reliability. “No single material can do everything well in a wireless device, so these 3D heterogeneously integrated systems are here to stay,” said Pradyot Yadav, a graduate student at MIT, in a press release. “If we can incorporate a material that manages the heat so the GaN and silicon are at the same temperature, then the reliability of the entire 3D chip will improve… By putting these GaN transistors into a diamond interposer, we are actually able to improve the performance of the device, as opposed to degrading it. We can get the best of both worlds.” The process starts by cutting prepared gallium nitride dielets out of a wafer, then drilling cavities in the single-crystal diamond substrate using a femtosecond laser. A die attach film is placed in the bottom of the cavities, followed by the dielet. Heat and pressure are applied to mold it with the film and diamond substrate. Additional dielectric and metal layers are then stacked on top of the GaN and diamond. The researchers used the technique to manufacture a power amplifier for wireless communications. “The power amplifier is the beating heart of a wireless device front end. Its performance will dictate the entire performance of your communication system. Our amplifier is powerful enough to ensure that a signal can be propagated for miles,” added Yadav. Applications could include high-power radars, space communications, industrial drones, and data center power conversion. [3] References [1] L. Mazzone, Y. Zong, H. Zhu, et al. Intrinsic polarization superjunctions in III-nitride heterostructures for efficient power electronics. Nat Electron (2026). https://doi.org/10.1038/s41928-026-01691-4 [2] H. Wang, S. Yan, Z. Xu, et al. Enabling thin p-GaN Ohmic contacts through ultrathin magnesium deposition and brief thermal annealing. Appl. Phys. Lett. 10 August 2026; 129 (6): 063306. https://doi.org/10.1063/5.0339815 [3] P. Yadav, X. Li, D. A. Baig, et al. A 4 W Heterogeneous Power Amplifier with GaN-on-Si Dielets in Single-Crystal Diamond Interposer for 6G FR3 Applications. 2026 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), Boston, MA, USA, 2026, pp. 411-414, https://doi.org/10.1109/RFIC70222.2026.11602311 The post Research Bits: Sep. 1 appeared first on Semiconductor Engineering.

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