circuits

Tiny transistor may become conductor king

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A microscopic image of a small gallium nitride-based device, which can be easily scaled up for higher current handling capability. Below, a larger version of a gallium nitride transistor. Researchers at Cornell University believe the device could form the basis for the circuitry in products from laptops to hybrid vehicles to windmills to other power electronic systems. (Credit: Junxia Shi)

CORNELL (US)—A newly developed and extremely efficient transistor may soon replace silicon as the semiconductor of choice for power applications.

Researchers believe the device could form the basis for the circuitry in products from laptops to hybrid vehicles to windmills to other power electronic systems.

The patent-pending electrical switch is made from the compound gallium nitride, a material with unique electrical properties that Lester Eastman, the John Given Foundation Professor of Engineering at Cornell University, has been studying for more than a decade.

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Details about the recent breakthrough were published in the journal Applied Physics Letters.

The new transistor’s on-resistance, or measure of resistance to electric current, is 10 to 20 times lower than today’s silicon-based power devices and has a high breakdown voltage.

High breakdown voltage is a measure of how much voltage can be applied across a material before it fails.

Researchers say the key to the device lies in gallium nitride’s low electrical resistance, causing less power loss to heat, and its ability to handle up to 3 million volts per square centimeter without electrical failure.

Silicon, a competing material, can handle only about 250,000 volts per square centimeter.

At the heart of improving electronics, Eastman says, is the ability to make devices that can switch electricity from high voltage to high current, which is a measurement of electrical applicability, while minimizing power loss.

“Power has to go from A to B in a machine with a high voltage transmission line to minimize power loss,” Eastman explains.

“Before now, there were no electronic devices that could handle both high current and the high voltage, but our device can do it.”

Eastman believes the transistors, which were made with Cornell nanofabrication equipment, might one day power everything from hybrid electric vehicles to Navy destroyers.

In fact, the U.S. Navy first funded Cornell’s research into gallium nitride transistors more than 10 years ago and is a major funder of Eastman’s research today.

In next-generation electrical devices, “you want to have the power that’s coming out to be not much less than the power that’s going in,” Eastman says. “This is the best material we know of that can do this conversion without loss of energy.”

The device was developed by Junxia Shi, a graduate student in Eastman’s lab. The New Jersey-based company Velox and Motorola spinoff Freescale have also helped fund the research, with the hope of producing the devices at an industrial scale.

Cornell University news: www.news.cornell.edu

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