Silicon electronics technology dominates information processing and offers a remarkable way to make very complex systems for very little cost. Many of the waveguide passive optical components used today in telecommunications such as wavelength splitters use the same technology base as silicon electronics — the silicon, silicon dioxide and silicon nitride that are the semiconductors and insulators of electronics become the waveguides of optics. Having one platform that could integrate electronics, optics and optoelectronics is an attractive idea, and if possible, the platform could transform the way that photonics technology is applied. However, silicon technology has a major weakness: It does not have strong optoelectronic effects that can be used to emit or modulate light. The mechanisms in silicon are very weak compared with those routinely used in optoelectronic devices made from the III-V semiconductors such as GaAs, InP and InGaAs. This weakness makes it difficult to put information onto light beams using silicon structures, whether for telecommunications applications or for emerging applications such as dense optical interconnects.

The III-V materials are difficult to integrate with silicon for a number of reasons, not the least of which is that they are the dopants that make silicon conducting. Other Group IV materials such as germanium, which is routinely integrated with silicon in modern electronics, might be tried, but none of those Group IV materials shares the same “direct gap” physics exploited routinely in III-V optoelectronics...

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