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KASSIOPEIA PROJECT Bundling unique European expertise for spaceborne devices

Editor: Jochen Schwab

Ferdinand-Braun-Institut, SweGaN AB, and the University of Bristol are partnering in the European Space Agency funded Kassiopeia project. The teams join forces to develop high-performance Ka-band GaN MMICs (monolithic microwave integrated circuits).

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GaN-on diamond HEMT
GaN-on diamond HEMT
(Source: University of Bristol)

In March, the Kassiopeia project was launched to provide a value-added chain using internationally leading technology only available in Europe. The consortium project, led by Ferdinand-Braun-Institut (FBH) in Berlin, aims to demonstrate a fully independent European supply chain, from silicon carbide (SiC) substrates, gallium nitride (GaN) epitaxy, GaN device processing up to power amplifiers. For this purpose, Ka-band MMICs using novel epitaxy, processing, and circuit concepts towards highly efficient GaN and aluminium nitride (AlN) devices will be developed and demonstrated. The Ka-band frequency band is used, for example, in satellite communications.

The CDTR at the University of Bristol’s research within this program focuses on direct thermal measurements on active GaN transistors by using micro-Raman thermography and advanced device characterizations and modeling. This will provide a continuous feed-back to all device and epitaxial developments planned in Kassiopeia.

FBH contributes its industry-compatible Ka-band MMIC technology on 100 mm GaN-on-SiC wafers. “The unique selling point of our GaN MMIC technology is its highly reproducible and reliable iridium sputter-gate technology”, emphasizes Dr. Joachim Würfl, head of FBH’s Power Electronics Department.

“This technique reduces dynamic losses (gate lagging) to values up to two times less than competing institutional and industrial technologies.” The technology is also known to significantly improve device reliability. Together with new approaches in terms of process technology and circuit concepts both targeting for parasitic loss reduction highly efficient Ka-band MMICs will be developed. The groundbreaking technology will thus provide advantages in performance and reliability, which are particularly important for spaceborne devices.

SweGaN participates with its unique buffer-free solution for GaN-on-SiC epiwafers, QuanFINE®, bringing its expertise in epitaxial layer design and optimization to the project. SweGaN will also supply in-house developed semi-insulating SiC substrates for evaluation. "We are excited to participate in this ESA-aligned project together with FBH and University of Bristol, shares Jr-Tai Chen, CTO, SweGaN. Conventional GaN-on-SiC materials for Ka band applications still lack maturity, leaving significant room for innovation and improvement. SweGaN will introduce its revolutionary epitaxial manufacturing process to address the challenge.”

The Kassiopeia project is funded under the ESA ARTES Advanced Technology Programme: “European Ka-band high power solid-state technology for active antennas”.

A sustainable energy grid for the future

A U.S. Department of Energy (DOE) award is empowering the Centre for Device Thermography and Reliability (CDTR) at the University of Bristol to create a resilient and sustainable electricity grid with the use of next-generation ultra-wide bandgap materials and devices.

The four-year, $12.4 million award from the DOE’s Office of Basic Energy Sciences, establishes a Research Center led by the University of Arizona, with the CDTR here in Bristol, the only non-US partner involved. Professor Martin Kuball, Director of the CDTR and Royal Academy of Engineering Chair in Emerging Technologies, says “we are excited to be part of this large US funded activity to enable the technology needed for so-called smart grids and helping our society to achieve zero carbon emission”. The Center will employ creative, multi-disciplinary scientific teams to tackle the toughest scientific challenges preventing advances in energy technologies, as well as investigating fundamental questions about ultra-wide bandgap semiconductors.

Ultra-wide bandgap semiconductors are for example aluminium nitride, boron nitride or diamond, which possess extraordinary physical and electrical properties. Devices constructed from them can operate at higher temperatures, voltages and frequencies than Silicon (Si), making them significantly more powerful and energy efficient than conventionally used Si-based power electronics. Through the use of ultra-wide bandgap materials, power substations could potentially shrink a hundredfold — to virtually the size of a suitcase — saving space and increasing the reliability of the grid. Wide band gap materials can also enable better integration of renewable energy sources into any electricity grid. While electricity grids traditionally only delivered power in one direction — from power plants to consumers — today’s grids must be flexible, giving and taking power as required. Renewable energy sources such as wind and solar power supply energy under the right conditions, but their cells and batteries require recharging when there is not enough wind or sun. A “smart grid” to meet these multidirectional demands is within reach, thanks to the research that the CDTR is doing.