ARCHIVED - Semiconductors in space: the final frontier

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August 08, 2008— Ottawa, Ontario

Last August, a high-tech prototype created by an NRC lab in Ottawa hitched a ride on the Space Shuttle Endeavour. A guest of Canadian astronaut Dave Williams, the "space tourist" was a gallium nitride wafer bearing high-frequency, high-power transistors.

The semiconductor's voyage was initiated by the Canadian Space Agency (CSA), which is keen on using gallium nitride devices for future space applications. "The CSA is doing reliability testing to see how our devices will stand up to extreme conditions in space," says Dr. Jennifer Bardwell, a senior research officer at the NRC Institute for Microstructural Sciences.

In August 2007, this gallium nitride wafer accompanied Canadian astronaut Dave Williams on the Space Shuttle Endeavour.
In August 2007, this gallium nitride wafer accompanied Canadian astronaut Dave Williams on the Space Shuttle Endeavour.

The CSA isn't the only organization with an interest in NRC's gallium nitride research. Dr. Bardwell's team is helping three Canadian companies exploit the promise of this technology to develop next-generation semiconductors. They include the Ottawa-based firms Gain Microwave and Taransys, as well as Emhiser of Parry Sound, Ontario.

Developed decades ago, gallium nitride (GaN) is a synthetic material that requires very high pressures and temperatures — over 800° C — to make. "But GaN is extremely stable and chemically inert — an attractive feature," says Dr. Bardwell. "You can put it in very harsh environments and it won't deteriorate. It's also an ideal material for high-power electronics because it can withstand high voltages."

Among its potential applications, GaN could be used in wireless base-station transistors, which need to handle very high power levels, or in hybrid vehicles for switching the energy source between electricity and gasoline. "Right now, that's done using silicon transistors, which have to be cooled," says Dr. Bardwell. "A hybrid vehicle has a radiator to cool the car and a separate cooling system for the electronics. With gallium nitride, you would no longer need the extra cooling system."

"Our specialty is growing single crystal layers of gallium nitride and then processing them into transistors and other semiconductor devices," continues Dr. Bardwell. Unlike other semiconductor materials, which are readily available as pure crystals, gallium nitride must be grown on top of other substrates — NRC uses silicon, sapphire and silicon carbide. "But it's a challenge to make a perfect crystalline layer on a different crystal," she adds. "There are often flaws in the material, which can lead to decreased performance and cracking."

"We're trying to improve the yield of GaN devices while increasing their reliability and reproducibility to make sure that everything works perfectly," Dr. Bardwell stresses. This is especially important in the fabrication phase. "The bigger the circuit, the bigger the challenge that we face," she concludes.

Enquiries: Media relations
National Research Council of Canada

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