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Light-Emitting Silicon Shines Much Brighter in New Invention
By John Markoff
New York Times

SAN FRANCISCO -- STMicroelectronics plans to announce a breakthrough on Monday in light-emitting silicon that could lead to a new generation of more powerful computing processors and more efficient automobile components as well as potentially higher-speed optical data-transmission systems.

The company, which is the world's third-largest chip maker, said that its researchers have succeeded in increasing the efficiency of light-emitting silicon 100-fold, for the first time making it comparable with conventional light-emitting diode materials like gallium arsenide. The first products are expected to reach the market later this year.

The researchers were able to increase the brightness of conventional silicon by implanting ions of rare-earth metals like erbium and cerium into a specially prepared layer on the surface of a silicon wafer. The technique yields a range of frequencies depending on the type of metal chosen. The company said that it had patented the techniques it used for implanting the materials.

"This certainly appears to be a novel approach," said Richard Doherty, president of Envisioneering, a computer industry consulting firm based in Seaford, N.Y.

The approach is aimed at using light to improve timing, an increasingly thorny challenge for the makers of the largest and most powerful silicon chips. Electronic timing circuits require that separate wires be used to deliver pulses to hundreds of thousands of points on each chip. As the chips become bigger and the wires become longer, delay times increase, adding complexity and limiting chip switching speeds.

"As we move toward placing entire computing systems on a single chip, the need to optically clock microelectronic circuits will become crucial," Mr. Doherty said.

But the possibility of delivering timing information optically has long been seen as a potential for dramatically increased processor speed.

"This has been the Holy Grail," said Dr. Rick Lytel, a physicist who heads Sun Microsystems' Physical Sciences Center and Advanced System Development Center. In the past, he said, the approach to the problem has been a hybrid one of combining different components, thereby adding complexity and limiting reliability and performance.

The first applications of the new technology will be to build power control devices in which the control circuitry is electrically isolated from the power switching devices, the company said. Currently such isolation can only be achieved by using external components, adding bulk and cost to designs.

Such applications have broad utility in the automotive industry; STMicroelectronics is a major supplier of devices that control motors and other systems in cars.

The company said it was also investigating the application of the technology to a kind of fiber optic communication networks called dense wavelength division multiplexing. By integrating the light source directly into the silicon circuits it is likely that significant advances in data network speed as well as lower cost will be possible.

The company said that in principle it would also be possible to build light sources based on the new technology. Today's L.E.D.'s based on gallium arsenide and similar materials are made at low costs and high volume, however, and it would be almost impossible for a new technology to compete, industry executives said.

Much of the research for the materials advance was done in an STMicroelectronics laboratory in Catania, Sicily. The company maintains several research centers in the region including research in the areas like soft computing employing fuzzy logic, nano-organics, molecular electronics, optoelectronics and micromachining.