How Gallium Nitride Could Help Power the World
One engineer's effort to cut electrical waste at the wall.
Umesh Mishra thinks day in and day out about power conversion—the trillions of adjustments in voltage, frequency, and current made daily to deliver electricity from wall outlets to computers, TVs, virtually any electronic device. And he thinks about the gadgets that do the converting, mostly built using silicon. Collectively, those converters waste nearly as much power in the form of heat as all the energy produced by all the renewable sources in the United States.
On average, silicon-based converters are only 90 percent energy-efficient. The 10 percent that is lost dissipates as heat between a plug and whatever a converter is powering. That’s why cell-phone chargers are warm to the touch, external power adapters for laptops heat up, and data centers chockablock with thousands of computer servers need a lot of air-conditioning.
Mishra is on a quest to find a better way through gallium nitride, a mix of nitrogen and gallium, a rare silvery-white metal found in trace amounts in zinc and bauxite ores. As the CEO of Transphorm, a gallium-nitride-technology company in Goleta, California, he’s banking on the idea that the elusive material can reduce energy loss to as little as one percent. Other companies and institutions are working with gallium nitride, but Transphorm is among the first to work with the high voltages that could yield the greatest cost savings.
Silicon-induced energy loss costs the U.S. economy $40 billion every year. “It’s a huge problem, and it’s invisible.”
“When gallium-nitride technology manifests itself to its full potential, the savings could equal taking the West Coast off the grid,” says Mishra, with characteristic ebullience. He estimates that the silicon-induced energy loss costs the U.S. economy $40 billion every year. “It’s a huge problem, and it’s invisible,” he says. “It’s a tax you don’t explicitly pay, but you pay every time you use an appliance. You pay for energy at the outlet, including all the waste as well.”
Mishra has been working with gallium nitride for many of his 23 years in the engineering department at the University of California, Santa Barbara. (He was elected to the National Academy of Engineering in 2009 for this work.) The compound, first grown as a single crystal film in 1969, drew widespread notice in 1993 when it was used to create bright blue light–emitting diodes, invented by Shuji Nakamura (who joined the U.C. Santa Barbara faculty in 2000). Mishra co-founded Transphorm in 2007 with a former student, Primit Parikh, now the company president, to focus on gallium nitride. So far, the company has received $105 million in seed money from the Department of Energy’s Advanced Research Projects Agency, Google, and other public and private entities.
But dethroning silicon—the planet’s third-most-abundant element after iron and oxygen—is no easy feat. Gallium is exceedingly rare, and gallium nitride has to be grown atom by atom in a controlled environment; inside Transphorm, employees don clean-room suits to coax gallium-nitride crystals to reach a few microns thick atop silicon wafers, which are then cut into chips. Gallium nitride devices for power converters are produced by the thousands each week; silicon devices are made by the billions in that period. With no real economy of scale, Transphorm devices cost considerably more than their silicon-based counterparts.
Dennis Monticelli, a technologist at electronics giant Texas Instruments, says media and industry talk makes it sound like silicon’s days are over, but that’s not the case. “Gallium nitride has more upside to it,” he says, “but it’s less mature, and we don’t know how far it can go.” The company does maintain a relationship with Transphorm. Jim MacDonald, a product manager at Texas Instruments, likens gallium nitride to a high-performance Corvette: For the price, he says, most people will opt to keep their Chevy.
But when Transphorm demonstrates its devices at trade shows, some people refuse to believe their efficiency, says Carl Blake, Transphorm’s marketing director. “We get a few who say ‘That’s not possible. How are you cheating?’” And this motivates Mishra to keep working toward a future in which data centers the size of football fields handle 10 times more traffic, electric cars have downsized to a single radiator, and external laptop power adapters have vanished.