Single crystal silicon-germanium-on-insulator for high density optical interconnects

The field of silicon photonics has seen a period of rapid technological advancement over the past decade, with significant interest and investment from both academia and industry. Progress is expected to continue, with global sales of silicon photonics products predicted to reach US$1 billion by 2020. A key motivation for silicon photonics is integration; achieved by using the CMOS compatible materials silicon and germanium. Here, we establish a silicon-germanium-on-insulator material platform using a rapid melt growth technique. We present a novel method for the fabrication of multiple, uniform composition localised silicon-germanium-on-insulator layers, demonstrating the ability to tune the composition of each layer by modifying the structural parameters of the layers, as shown in Fig. 1. This is achieved using only a single Ge growth step and a single anneal step, therefore dramatically reducing fabrication cost and complexity when compared with traditional epitaxy techniques.We investigate the regrowth mechanism exhibited by this rapid melt growth technique, and study the effects of the structural parameters of the tailored structures on the SiGe composition profiles. Using this material platform we can potentially exploit the tunable bandgap of the SiGe alloy for wavelength division multiplexing applications, with the potential to form low power electro-absorption modulators with an extremely high bandwidth density when compared to other modulator device designs. In addition, we discuss extending silicon photonic circuits into mid-infrared wavelengths, and identify the potential applications of such systems.We present some early results from passive mid-infrared photonic devices on a silicon-on-insulator platform.