In an advance that could lead to lighter spacecraft and smarter cars, researchers have developed a new technique for producing a high-quality semiconductor that's much more resistant to extreme conditions than the silicon found in most of today's electronics.
Devices built with the rugged material would not require cooling and other protections that add size, weight and cost to traditional silicon electronics in power systems, jet engines, rockets, wireless transmitters and other equipment exposed to harsh environments.
And because the material — silicon carbide — can be made with fewer flaws than ever before, more reliable and more complex electronics can be built with it, according to the Japanese researchers who reported their findings in Thursday's journal Nature.
In fact, the discovery paves the way for commercial adoption of the material that's stymied engineers for decades, said Roland Madar, a physics professor at the National Polytechnic Institute in Grenoble, France, in a commentary accompanying the research.
"These results are spectacular: The ... process is a major innovation in materials science," he said. "Silicon carbide has become, at last, a contender for silicon's crown."
Still, the Japanese researchers, led by Daisuke Nakamura of Toyota Central R&D Laboratories Inc., believe practical uses are at least six years away, said Masato Kimura, a spokesman for the lab based in Aichi, Japan.
The problem with silicon — the basic building block of most electronics today — is that it becomes less reliable and less efficient when exposed to high temperatures or radiation.
Silicon carbide, which is so resistant to heat that its used to protect the space shuttles, is a semiconductor like silicon. It's also nearly as hard as diamonds.
But those unique properties make it difficult to use in electronics. Because it doesn't become liquid under high heat, it can't undergo the traditional process that silicon undergoes to form ingots that are turned into nearly flaw-free wafers.
Instead, single silicon carbide crystals are formed by the condensation of supersaturated vapor. The process, which has been around since the 1970s, leaves many tiny structural defects, and the result is not good enough for complex devices like microprocessors or memory chips.
In fact, silicon carbide-based electronics today are simple diodes that are used in niche products such as power systems. Traditional silicon-based computers in extreme environments — whether in space or in a car — must be protected from extreme environments.
"If you need electronics at high temperatures, you need significant cooling," said T.S. Sudarshan, an electrical engineering professor at the University of South Carolina not affiliated with the research. "The size of the cooling systems will exceed the size of the device and that's the problem."
The Japanese researchers discovered that they can build silicon carbide wafers by using a multiple step process in which the crystal is grown in several stages. As a result, defects are minimized.
Using the technique, the researchers were able to build near-perfect wafers of up to 3 inches in diameter. There's still considerable work to be done to catch up with traditional silicon: The semiconductor industry today uses silicon wafers of up to 12 inches in diameter.
"Granted this may not be large volume for commercial (use), but even on a demonstration basis this is very significant," Sudarshan said.
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