Record efficiency for satellite GaN transistor
Researchers at Fraunhofer IAF have developed a GaN transistor technology with a gate length of 70 nm that achieves record efficiency values under typical satellite conditions.
“With our innovative technology, we are making an important contribution to the establishment and expansion of seamless and resilient global communication networks,” explains Philipp Döring, scientist in the Technology Department at Fraunhofer IAF and lead author of a research paper presenting the 70 nm GaN HEMTs.
Döring will present the paper 'High efficiency and high linearity 70 nm GaN technology for future SatCom applications' on September 23 from 2:10 pm to 2:30 pm at the European Microwave Integrated Circuits Conference (EuMIC) in Utrecht, Netherlands, during European Microwave Week (EuMW).
The GaN HEMTs were developed, manufactured, and characterised in the in-house semiconductor line in the Epitaxy, Technology, and Microelectronics departments at Fraunhofer IAF. The GaN/AlGaN semiconductor material system was grown on semi-insulating 4-inch SiC substrates using MOCVD. Processing was carried out using electron beam lithography, among other methods.
The researchers performed test measurements on individual transistors as well as directly on the wafer. In small-signal measurements, a cut-off frequency of fT = 122/95 GHz and a maximum frequency of fMAX more than 350 GHz were determined at VDS of 7/15 V. Load-pull measurements yielded a maximum power-added efficiency of 58.6 percent and a maximum output power of 2.46 W/mm at 38 GHz on 8x60 µm transistors.
To determine signal linearity, the researchers used a two-tone load pull method to test which of the 70 nm GaN HEMT meet the requirements currently specified by the European Space Agency (ESA) for satellite communications. Under the boundary condition of IMD3 ≥ 30 dBC, the technology achieved an efficiency of PAE = 54.4 percent and an output power of 1.01 W/mm. This is the highest efficiency value ever measured for a GaN technology at 30 GHz.
The results were obtained as part of the Magellan and GANYDEM170 projects. Magellan is funded by ESA and aims to develop highly efficient mmWave GaN high-power amplifiers for GEO and LEO active antenna applications. GANYDEM170 is funded as an IPCEI (Important Project of Common European Interest) by the German Federal Ministry for Economic Affairs and Energy (BMWE) and enables the realisation of an industry-ready mmWave GaN technology for metrology applications.
At EuMW 2025, which will take place from September 21 to 26 in Utrecht, Netherlands, Fraunhofer IAF will present further research results from the field of GaN-based high-frequency electronics in addition to the findings of Philipp Döring.
