Silicon Starts to Shine

Light Reading
News Analysis
Light Reading
11/20/2003



A development that could eventually lead to massive cost reductions for many types of optoelectronic component has been announced by a small team of researchers at the U.K.’s University of Surrey. Two years ago, the team managed to make silicon act as a light source, something that hadn’t been possible up until then (see Light From Silicon). But at the time, there was a snag: The silicon could only generate light at a wavelength of 1100 nanometers (nm), which wasn’t suitable for telecom applications.

Now, the team has got over the problem. It’s optimized the fabrication process to produce light emissions at any wavelength out to 1700 nm -- covering both 1310 and 1550 nm, which are the two key regions for optical fiber transmission.

This opens up the possibility of integrating optics and electronics on the same communications chip, and making use of the wealth of silicon manufacturing technologies that already exist in the semiconductor industry. The bottom line could be big cost reductions.

The team, led by Prof. Kevin Homewood, has established a startup called Si-Light Technologies Ltd. (Website registered but not active) to commercialize the technology (see Si-Light Unveils Silicon LEDs)

Si-Light has recently been awarded a grant worth £60,000 (about US$100,000) from the U.K. government's Department of Trade and Industry to investigate market opportunities for its technology. That's made it possible to employ a Project Manager, Dr. Peter Epperlein, whose task is to investigate potential industrial partnerships across all types of industry, not just telecom.

"I have at least 40 companies in my list," says Epperlein, who claims to have good contacts in Europe thanks to his long service at IBM Research in Ruschlikon, Switzerland, Agilent Technologies Inc. (NYSE: A), and later JDS Uniphase Corp. (Nasdaq: JDSU; Toronto: JDU). Out of the 15 firms he has approached so far, "several" want to pursue the technology further and have signed NDAs (non-disclosure agreements), he says.

Si-Light is not the only company investigating light-producing properties of silicon. Just last week, Translucent Photonics Inc., a majority-owned subsidiary of Australian corporation Silex Systems Ltd., said it had produced "optical gain" in silicon (see Silex Claims Silicon Breakthrough). But when contacted, the company declined to provide further details at this time. It is not clear what wavelength of light was produced, or even if the company has made a working device.

It's also worth mentioning STMicroelectronics NV (NYSE: STM), which last year produced high-efficiency light sources using erbium-doped silicon-rich oxide -- a material that is wholly compatible with modern silicon manufacturing methods (see Erbium-Doped Chips?). The company says it plans to have a product available in 2004, for chip-to-chip interconnections -- which is also likely to be the first application for Si-Light's technology too.

Si-Light's approach is to implant ions in silicon. That means shooting ions at the silicon with enough energy so they get embedded below the surface. Each ion creates a "dislocation loop" around it -- rather like a ripple around a pebble thrown in a pond -- which creates local stress in the material and prevents the movement of electrons. If electrons can travel around, they meet up with defects in the crystal, which allow them to lose energy as heat instead of light. Preventing this process is the key to getting light out.

Homewood and his team have spent the last two years refining the ion implantation process using different elements and different process parameters. Using different ions makes it possible to get different wavelengths of light out of silicon. "Now we have the correct recipe," says Epperlein.

— Pauline Rigby, Senior Editor, Light Reading

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