Silicon-germanium by rapid melt growth for the silicon-on-insulator platform

Abstract

Silicon-germanium (Si1-xGex) and Ge are widely used in optoelectronics. It is fully miscible across the whole composition range, which allows for the whole spectrum of the band gap to be tuned between the values of pure Si and pure Ge. This versatility is extremely important for photonics applications such as electro-absorption modulators and photodetectors, where the operating wavelength is strongly dependent on the Si content. Traditional SiGe growth allows only a single SiGe composition to be grown across the wafer. On the contrary, Rapid Melt Growth (RMG) offers the opportunity of multiple compositions of SiGe by using just a single Ge deposition step and a single anneal step, as previously demonstrated on the silicon platform. This is made possible by engineering the structural parameters of the RMG structures to enable multiple uniform composition strips of SiGe across the wafer, each with a different, tuneable composition. Furthermore, RMG can be used for the growth of high-quality SiGe material with a smaller number of defects than other growth techniques, which can lead to the fabrication of higher performance active devices. Finally, the simplicity of the fabrication process provides a cost-effective growth method making this concept very attractive. In this thesis, for the first time, RMG processing was successfully used to demonstrate constant composition SiGe and Ge structures (in range between 65 and 100% Ge) embedded within Silicon-on-Insulator (SOI)substrates. The structures embedded in the SOI platform enable integration to waveguides for the creation of both passive and active waveguide-based devices to form complex Photonic Integrated Circuits (PIC). This first demonstration promises to allow the development of new devices and associated applications with high performance and low cost. The findings of the research will lead to waveguide integration and work on active devices.

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ORCID for Frederic Gardes: orcid.org/0000-0003-1400-3272

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