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To: Pullin-GS who wrote (273)	9/23/2003 11:58:25 AM
From: tech101	Read Replies (1) \| Respond to of 290

Light emitting silicon close to commercialization, says ST By Peter Clarke Silicon Strategies 09/23/2003, 10:17 AM ET CATANIA, Italy -- STMicroelectronics said Tuesday (September 23, 2003) it has increased by a factor of 50 the power output of its previously announced light-emitting silicon technology and that it should be able use the technology make optocouplers in the near term. Silicon's ability to detect light signals has been long known and the material has been successfully deployed in discrete sensors and more recently in arrays of charge-couple devices and photodiodes as camera chips. But due to its band-gap silicon is not a natural emitter of light. This property has been reserved for compound semiconductors. However with nanometric structures made of silicon and nanometric films on semiconductors, having an influence on the band-gap, a number of research papers have been presented on light-emitting silicon since early work with porous silicon at the beginning of the 1990s. In 2002 ST said it had achieved an efficiency of light emission 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 (see October 28, 2002, story). ST's light emitting silicon is based on the implanting of ions of rare-earth metals such as erbium or cerium, in a layer of silicon rich oxide (SRO), such as silicon dioxide enriched with silicon nanocrystals of one or two nanometers diameter. "Since then, ST has made substantial further progress towards turning this pioneering research into both near-term commercial products and potentially disruptive new technologies," said Salvo Coffa, a research director within ST's Corporate R&D organization, in a statement. In the last year Coffa's team have increased the external quantum efficiency of its light-emitting devices by a factor 1.5 and increased the maximum emitted power by a factor of 50, the company said at a technology seminar intended to present R&D and manufacturing activities. As a result, ST is now able to produce more than 1-milliwatt of emitted light power for each square millimeter of silicon, the company claimed. Although the market for optocouplers is well established, based on discrete compound semiconductor emitters, a more significant aspect of ST's research would be the ability to be able to monolithically integrate all necessary elements -- light emission, light waveguides and light detectors -- for optical processing on a silicon chip. ST has produced a prototype silicon optocoupler that it said delivers 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 the same statement. He added: "Given that we already know from our current research that it will be possible to increase this performance by at least another order of magnitude, we are on the threshold of opening up entirely new industrial applications in the fields of displays and even solid state illumination. In addition to targeting the large existing market for conventional optocouplers, ST will be aggressively pursuing these novel applications," said Coffa.