Power Electronics

STMicroelectronics Extends Lead in Light-Emitting Silicon

At a technical seminar devoted to some of its leading edge R&D and manufacturing activities, STMicroelectronics (ST) recently disclosed further significant advances it has achieved in the field of light-emitting silicon technology. Among other applications, the enhanced technology will allow ST to enter the market for optocouplers in the near future.

Last year, ST announced a breakthrough technology that allowed silicon-based devices to emit light with an efficiency that was some two orders of magnitude better than the best previously achieved results with silicon, allowing these devices to reach, for the first time, efficiencies comparable to those of more expensive compound semiconductors while retaining the cost advantages of high-volume silicon technology.

"Since then, ST has made substantial further progress toward turning this pioneering research into both near-term commercial products and potentially disruptive new technologies," said Dr. Salvo Coffa, research director of the SST (Soft Computing, Si-optics and post-silicon Technologies) group within ST's corporate R&D organization. The results announced by ST in October 2002 already went far beyond the existing state-of-the art in silicon-based light emission, making ST the first semiconductor manufacturer in the world to be in a position to consider the integration of Si-based light emitting technology into products such as optocouplers, for which there is already a substantial world market based on more expensive nonsilicon technologies, as well as entirely new types of product that exploit ST's ability to integrate the all three functions of light emission, light waveguides and light detectors on a single silicon chip that can be manufactured at low cost on high-volume production lines.

Already, ST has produced fully working prototypes of a completely silicon-based optocoupler that demonstrate that all-silicon devices can deliver similar performance to that of traditional devices while offering the cost benefits of silicon manufacturing.

"Comparing the performance of our first prototypes with that of existing devices and considering the improvements we have already made to the initial technology, we expect to reach the commercial crossover point in around six months," said Coffa.

In fact, Coffa's team has not only increased the external quantum efficiency of its light-emitting devices by a factor 1.5, which already exceeds the quantum efficiency of traditional semiconductor materials, but also increased the maximum emitted power by a factor 50. As a result, ST is now able to produce more than 1 mW of emitted light power for each square millimeter of silicon. For more information, visit www.st.com.

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