Revolutionizing Wireless: New GaN Power Amplifier Boosts Efficiency, Cuts Consumption for Communication and Radar

March 5, 2026

Fujitsu R&D teams have successfully developed a technology achieving a world-record* power conversion efficiency of 74.3% at an 8-GHz frequency for a power amplifier, which is essential for long-range radio wave transmission and broadly applicable in wireless communication, radar, and other fields. This frequency band is part of FR3 (1), a candidate frequency band for the 6th Generation mobile communication system (6G), and is also known as the X-band (2), widely used in various radar systems. This achievement was made possible by developing a high-quality insulated gate technology for gallium nitride (GaN) (3) high-electron-mobility transistors (HEMTs) (4), enabling both high efficiency and high output power. This technology will contribute to realizing a sustainable society by reducing power consumption in wireless devices and lowering CO2 emissions.

The details of this technology will be published in the academic journal ”Applied Physics Express".

* Based on our company survey

Background

Our convenient society is supported by invisible radio waves. Wireless communications tools like smartphones and Wi-Fi, radar used for weather and defense, public broadcasting like TV and radio, and non-contact heating represented by microwave ovens have all become indispensable. These technologies utilize different frequencies, which result in variations in the radio wave's range, ease of diffraction, resolution, and the size of peripheral equipment, among other characteristics, ensuring that the most suitable frequency is used for each application.
Meanwhile, with the recent advancements in digitalization and the widespread adoption of AI, communication traffic has surged. Among these, wireless communication with mobile objects such as people and vehicles is fundamentally disadvantaged compared to wired communication, such as optical fibers, in terms of communication speed and power consumption. Therefore, continuous performance improvement is required.

Conventional Challenges and Our Developed Technology

GaN-HEMTs offer superior output power and efficiency compared to transistors based on other materials such as silicon and gallium arsenide, leading to their widespread use as power amplifiers in mobile communication base stations and various radar systems. Conventional GaN-HEMTs have employed Schottky barrier junction (5) gate electrodes, where metal and semiconductor are directly contacted, to control current. However, a significant challenge with this structure has been the onset of leakage current during high-power operation, particularly under high voltage and large current conditions. This leakage current ultimately leads to a degradation in both output power and efficiency.
To suppress this leakage current, we have developed a metal-insulator-semiconductor (MIS) type structure (Figs. 1, 2) by inserting an insulating film made of silicon aluminum nitride (SiAlN) between the gate metal and the GaN semiconductor. The SiAlN film can be grown using the same metal-organic chemical vapor deposition (MOCVD) (6) method as the GaN semiconductor. By forming the SiAlN immediately after the crystal growth of the semiconductor, it becomes possible to achieve high quality not only in the insulating film itself but also at the insulator/semiconductor interface. Furthermore, by stacking two different layers of SiAlN and SiN, we formed an overhang structure called a gate field plate, which suppresses electric field concentration during high-voltage operation. Thanks to these technologies, we simultaneously achieved a power-added efficiency (PAE) (7) of 74.3% and an output power density of 9.8 W/mm at 8 GHz, within FR3 and X-band (Fig. 3). As of March 4, 2026, this PAE is the world's highest for X-band power amplifiers with an output of 5 W/mm or more (Fig. 4).
Additionally, when this device was evaluated at 3 GHz, a frequency close to those used in 4G and 5G, it achieved a PAE of 80.6% and a power density of 10.5 W/mm, demonstrating the applicability of this technology to a wide range of frequencies.

Future Outlook

Going forward, our company will proceed with the development of implementation technology and the evaluation of reliability, aiming for the practical application of this technology. Furthermore, by applying this technology to high-frequency devices such as millimeter-wave and sub-terahertz-wave devices, we will contribute to solving global environmental issues – one of our company's corporate materialities – by reducing the power consumption of wireless equipment across a wide frequency range.

Fig. 1 Cross-sectional schematic view of GaN-HEMT with MIS gate.

Fig. 2 Gate characteristics of GaN-HEMT

Fig. 3 Power characteristics of GaN-HEMT

Fig. 4 Benchmark of X-band power amplifiers

Note

(1) FR3 (Frequency Range 3):
This is a frequency band (7.125 GHz to 24.25 GHz) internationally under consideration as a candidate frequency for next-generation mobile communication systems, positioned between the current FR1 (sub-6 GHz band) and FR2 (millimeter-wave band).
(2) X-band:
One of the microwave frequency classifications that designates the 8 to 12 GHz band.
(3) Gallium Nitride (GaN):
One of the wide-bandgap semiconductors highly resistant to voltage breakdown. Compared to other wide-bandgap semiconductors such as Silicon Carbide (SiC) and Gallium Oxide (Ga2O3), GaN has the characteristic advantage of achieving high electron mobility by adopting the HEMT structure.
(4) High Electron Mobility Transistor (HEMT):
A field-effect transistor that utilizes the phenomenon where electrons at the interface of semiconductors with different bandgaps move at higher speeds compared to those in conventional semiconductors. Fujitsu Limited pioneered its development in 1980, and it is now widely used as a foundational technology supporting our ICT society, including applications in satellite broadcast receivers, mobile phone base stations, and GPS-based navigation systems.
(5) Schottky barrier junction:
A type of metal-semiconductor junction that exhibits rectifying properties, allowing current to flow in only one direction. It is utilized in the gate electrodes of field-effect transistors.
(6) Metal Organic Chemical Vapor Deposition (MOCVD):
A crystal growth method used to form atomically flat thin films. It utilizes metalorganic compounds such as trimethylgallium as precursors.
(7) Power-Added Efficiency (PAE):
One of the indicators representing power conversion efficiency. It shows how much of the input DC power contributed to the amplification of the signal.