New semiconductor readied for mass production.

• Author: Jean, Grace V.
• Position: Inside Science + Technology

To detect and track fast-moving threats, military radars need to transmit radio signals at high frequencies. The workhorse material that enables the amplification of those signals may yield its crown to a new semiconductor that promises leaps in power capability and performance.

Researchers have been developing gallium nitride semiconductors for nearly two decades. When grown on silicon carbide substrates, the gallium nitride transistors can operate at higher power than the gallium arsenide circuits currently found in a number of U.S. weapons, including phased-array radars aboard platforms ranging from fighter jets to ground-based missile defense systems.

Gallium arsenide chips today are embedded inside the radars' transmit and receive modules. Several semiconductor chips per module help to boost RF signals that are radiated from the antenna, bounced off targets and terrain and then received by the system and filtered through low-oise amplifiers for processing.

"Gallium nitride gives us that flexibility of not only dramatically improving the performance of power output, but also simultaneously allowing us to shrink the sizes of the components, which allows us to reduce the cost of the system," said Colin Whelan, technical director of advanced technology at Raytheon Co.'s Integrated Defense Systems.

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Raytheon in 2000 began investing in the technology, which had gained material quality improvements in part from the use of gallium nitride in green, blue, violet and white light-emitting diodes, or LEDs. Scientists fabricated gallium nitride semiconductor wafers in increasingly larger sizes, from 2-inch diameter silicon carbide substrates to 4-inch wafers to match the existing gallium arsenide material standard. Raytheon in 2009 established a process for fabricating the 4-inch gallium nitride wafers at its Andover, Mass., foundry, where it has been producing gallium arsenide chips for about 20 years. Engineers there are now building gallium nitride wafers and incorporating them into modules for defense applications.

"We have all the process design tools and the statistical models in place to build these circuits and predict performance even before we build," said Whelan.

Gallium nitride is a semiconductor that has a "wide band gap," meaning that it can operate at high voltage to generate power. It produces five times the power of gallium arsenide. If it replaced gallium arsenide devices in existing radars, the chip would...