Building computer chips is fraught with trade-offs. To make faster chips, engineers cram transistors closer together. But they're approaching the point where circuits will be so tightly packed that signals will interfere with each other. So scientists want to develop optoelectronic chips. These will use light pulses to carry signals--an advantage because light beams pass through each other with no interference.
Researchers first tried combining silicon switches with tiny laser diodes made of gallium arsenide. But the combination is extremely difficult to manufacture. Now, they're making startling breakthroughs using a better choice: silicon and germanium, a duo pioneered by IBM. Last summer, Princeton University Professor James C. Sturm made a silicon-germanium device that produced a faint beam of light--at room temperature, not the chilly 238F temperatures needed by most similar diodes. And University of Tokyo scientist Yasuhiro Shiraki recently built a silicon-germanium chip that emits a strong beam of light at room temperature.
Shiraki says it will take at least five years to commercialize chips with integrated electronic and optical functions. But the rewards could be fantastic. He envisions chips that are much faster than any on the drawing boards today.