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European GaN devices to go into orbit

Apr 11, 2013
For the first time, a European gallium nitride based device will fly into space. It will monitor environmental occurrences in places such as the rain forest and the sea
When satellite Proba-V flies into space in the coming weeks to begin its earth observation, a device based on the semiconductor GaN will be on board.

Being more robust, more compact and lighter than traditional solutions, the new technology promises to significantly improve communication electronics in space.

In the course of an intensive test series, the amplifier developed by the Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg has qualified itself for the journey into space.

The satellite which the European Space Agency ESA will launch into space for earth observation weighs about 140 kg and is only roughly the size of a washing machine. The mini-satellite Proba-V is covered in solar cells and will be observing the vegetation on earth. Every other day, the environmental satellite will send pictures from a distance of about 820 km. Rain forest destruction, pollution of the seas and soil erosion will be made visible by pictures taken in various spectral ranges.

The mini-satellite Proba-V ( ESA – P. Carril)

"GaN has the potential to revolutionise communication in space. We expect signal strength and data transmission to improve five or tenfold," says Andrew Barnes, who is responsible for the project at ESA. "We are eagerly awaiting the results of the first practical test in space".

The institute in Freiburg has developed an amplifier circuit for the frequency range of 8 - 8.5 GHz (X-band) for the communication system of Proba-V. Tesat-Spacecom in Backnang, in cooperation with SCHOTT Electronic Packaging, then packaged the GaN amplifier together with further components into a hermetically sealed housing suitable for space travel.

GaN in stress tests: robust and reliable

GaN devices can be operated under much higher voltages and temperatures than traditional silicon or GaAs components. The circuits are more compact, smaller and lighter than other solutions.

They might even replace electron tubes currently used for amplification. This would significantly reduce weight and transport costs, which can amount to €30,000 per kilogram of payload. Due to the long lifetime and radiation hardness of the semiconductor material, such electronic devices are ideally suited for the extreme conditions posed by aerospace.

Before being admitted for space travel, however, the GaN device had to prove its resilience. The device was exposed to cold and heat, strong vibration and motion as well as radiation.

"Accelerated lifetime tests, conducted together with Tesat-Spacecom, have shown that our GaN amplifier will live for at least 20 years", says Patrick Waltereit, project leader at Fraunhofer IAF. "The approval of our device for the flight into space is an important milestone for the further development of GaN technology, also for other areas of application".

Power semiconductor pushes the limits of silicon technology

Due to its exceptional physical properties, GaN is ideally suited for applications in power electronics.

Compared to conventional semiconductors such as silicon and GaAs, GaN possesses a larger bandgap (3.4 eV) and higher breakdown field strength (3.3 MV/cm). Higher dielectric strength and current density result in a fivefold increase in power density.

What's more, the usable frequency range is larger in GaN, which allows several functions to be integrated on one chip.

The thermal robustness of the semiconductor results in a considerable decrease of cooling effort, which is both energy- and cost-efficient. This makes compact and energy-efficient GaN devices interesting not only for applications in aeronautics, but also for voltage converters for the batteries of electric cars, solar panels or household appliances. As such, these devices offer high potential especially for applications which demand high performance and long lifetime even in harsh environmental conditions. This is where silicon technology meets its limits.

GaN based processed X-band amplifier circuits. The circuit for Proba-V has a size of 2 x 3.5 mm2 ( Fraunhofer IAF)

The project

The European Space Agency ESA founded the initiative Great ("GaN Reliability Enhancement and Technology Transfer Initiative") in order to exploit the potential of GaN technology for aeronautics.

Together with industrial partners, renowned research institutes in the field of III-V semiconductors, such as Fraunhofer IAF, develop high quality GaN-based devices under the project leadership of Tesat-Spacecom, thus strengthening the competitiveness of the European aerospace industry.

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