Germanium Quantum Wells for High-Performance Modulators in Silicon Photonics

Silicon electronics dominates information processing, and offers a remarkable technology for making very complex systems for very little cost. Many of the waveguide passive optical components that we use today in telecommunications, such as wavelength splitters, use the same technology base – the silicon, silicon dioxide and silicon nitride that are the semiconductors and insulators of electronics become the waveguides of optics. The idea of one platform that could integrate everything – electronics, optics, and optoelectronics – is particularly attractive and could transform the applications of photonics. But silicon technology has a major weakness: it does not have strong optoelectronic effects we can use for emitting or modulating light. The mechanisms in silicon are very weak compared to those we use routinely in optoelectronic devices made from the III-V semiconductors like GaAs, InP, and InGaAs. This weakness makes it difficult to put information onto light beams using silicon structures, either for telecommunications applications, or for emerging applications like dense optical interconnects.