The End of Silicon May Be in Sight

Silicon Valley's name may as well be Steam Locomotive Alley if some scientists have their way — they have come up with a way to replace the silicon used in semiconductor chips with another element called gallium, producing much faster circuits.

But hurdles remain in getting products to market.

Gallium (especially gallium arsenide, known to chemists as GaAs) has been studied for three decades as a replacement for silicon, since its higher "electron mobility" should produce faster transistors and therefore faster computers, explained Christopher Hinkle, a materials scientist at the University of Texas. This is especially true of a three-way combination of indium (a rare, silvery metal), gallium (another rare silvery metal that in pure form melts at room temperature), and arsenic (a notorious poison that can also serve as a hardening agent).

Mixing them and using the product instead of silicon as the foundation for a semiconductor chip, Hinkle has found, can indeed produce transistors that are 10 times faster than the silicon versions.

Tricky chemistry

Gallium transistors have always run afoul of the electrical interference generated by what he called the substance's "tricky surface chemistry." Basically, Hinkle has found that the gallium on the surface forms an oxide (rusts, in other words) and the resulting layer of gallium oxide creates endless reliability problems, he told TopTenREVIEWS, since what he called "dangle chemical bonds" affect how electrical charges move.

"We have already made transistors using the indium-gallium-arsenic material, and they are right around 10 faster than silicon ones," he said. "But they have an order of magnitude more defects, making them less reliable, and they break down faster."

However, Hinkle will be presenting a paper next week at the 56th annual International Symposium & Exhibition of the American Vacuum Society (November 8-13 in San Jose) proposing a solution: coat the material with silicon, or with a less troublesome variant of gallium oxide.

"It's harder than it sounds — the whole process has not been completely solved," he said.

The reality

Oxygen is part of the air and so preventing surface oxidation before some other coating is applied is difficult. Meanwhile, the more troublesome variant of gallium arsenide is (of course) the one with the strongest, most stable chemicals bonds, Hinkle said.

He expects that indium-gallium-arsenic circuits will show up in high-end desktop computers, hopefully within a few years. But he did not expect them to automatically be ten times faster than silicon-based machines. The designers may elect to maintain the same speed while running at one-tenth the wattage, or use the same wattage at ten times the speed — or some combination.

Since more watts means higher operating temperatures, and since computer CPUs are already pushing practical temperature limitations when running faster than 4 gigahertz, he expects the designers will lean a little more toward less wattage rather than higher speed, and the result will be systems that are about three times faster.

This article was provided by TopTenREVIEWS.