Power electronics is a rapidly growing field crucial in many industries, from renewable energy to electric vehicles. Among the key components of power electronics systems are power transistors, which control the flow of electricity in various applications. Transphorm has developed a new type of transistor, the SuperGaN FET, that has the goal to enhance the performance of gallium nitride power transistors in cascode configuration.

Transphorm took a 280-W GaN gaming laptop charger and dropped in pin-to-pin–compatible SuperGaN devices, replacing the paralleled GaN devices shipped in the adapter. Philip Zuk, SVP of business development and marketing at Transphorm, said during APEC 2023 that SuperGaN provides higher power efficiency.

SuperGaN FETs

Gallium nitride is a wide-bandgap semiconductor that offers several advantages over traditional silicon-based devices, including higher efficiency, faster switching speeds and higher power density. According to Transphorm, its SuperGaN FETs are designed to offer the following features:

High efficiency: These transistors are designed to be up to 40% more efficient than traditional Si-based transistors. This means they waste less energy and generate less heat, which can lead to longer device lifetimes and reduced cooling requirements.

High reliability: Transphorm’s SuperGaN FETs are designed to be highly reliable, with a failure rate that is reported to be orders of magnitude lower than traditional Si-based transistors.

High voltage: These transistors are designed to operate at high voltages, with a DC breakdown voltage of up to 650 V and a transient of 800 V. This makes them suitable for many high-voltage power-conversion applications, including EVs, renewable-energy systems and industrial equipment.

Easy to drive: Transphorm’s SuperGaN FETs are designed to be easy to drive, with a low gate charge and a wide safe operating area. This means they can be used with various gate-drive circuits, making them ideal for various applications.

Increased device lifetime: These transistors generate less heat than traditional Si-based transistors, leading to longer device lifetimes and reduced cooling requirements.

Higher power density: These transistors are more efficient than traditional Si-based transistors, so they can achieve higher power densities.

Transphorm and other companies, such as Nexperia, manufacture cascoded devices. The primary benefit of this strategy is the gate drive. Because a Si MOSFET is being driven with threshold voltages in the 3- to 4-V range and a gate oxide with a typical rating of ±20 V, the driver has a wide operational window, while the cascode has a robust safety margin and excellent noise immunity. Unipolar gate drivers, such as those utilized for Si applications, may be used. In addition, the presence of the freewheeling Si MOSFET body diode and the cascode circuit’s lower temperature coefficient to RDS(on) are advantageous in high-temperature and -current applications. In a cascode circuit, gate leakage can be up to two orders of magnitude less than in a typical e-mode device. As a result of the increased gate margins, more thermally efficient TO-247 packages are available. Automotive AEC-Q101–qualified devices are available. Output capacitance, reverse-recovery loss from the Si MOSFET body diode and less slew rate control due to a percentage contribution from the RDS(on) of the Si device are some disadvantages of the cascaded approach.