Silicon photonics offers great benefits in terms of cost, performance and power consumption. This is increasingly important as the demand for internet bandwidth continues to grow. Optical detection in silicon photonics is performed via the integration of germanium, one of the more challenging integration steps during fabrication. This thesis describes research into a novel technique to grow silicon-germanium on silicon and its application in waveguide detectors and research performed into the application of germanium at extended wavelengths of light. Chapter 1 provides a brief introduction to silicon photonics and chapter 2 covers background material on p-n and p-i-n detectors as well as germanium growth on silicon and it’s applications in silicon photonics. Chapter 3 presents work done on a germanium condensation technique using high fluence ion implantation, suitable for straightforward silicon-germanium fabrication. Using this technique a crystalline layer of silicon-germanium with a high concentration of 92% germanium was demonstrated. In addition a semi-empirical model was developed using a segregation coefficient, an enhanced linear oxidation rate and transient enhanced diffusion. This technique was then used to fabricate a photodetector for operation at a wavelength of 1310 nm. While the responsivity of the detector of 0.01 A/W was modest, this work presents the first demonstration of a detector fabricated in this way, and as such provides a foundation for future improved devices. Chapter 4 presents work done on p-i-n germanium detectors to increase their detection limit in the thulium doped fibre amplifier band. This work originally focused on using mid-bandgap lattice defects introduce via ion implantation to improve the detection limit.
However, during this experimental work it was determined that the unimplanted samples had a responsivity of 0.07 A/W at 1850 nm and 0.02 A/W at 2000 nm which was higher than that of the defect implanted samples and so the unimplanted samples were investigated further. From this work it was found that the absorption of the germanium detectors was 0.003 μm-1 at 1900 nm, which is approximately a factor of 10 greater than that of bulk germanium. The increased responsivity and absorption coefficient were attributed to tensile strain in the germanium. In Chapter 5 Raman spectroscopy was employed in order to investigate the detectors described in chapter 4 and confirm the presence of tensile strain. When compared with Raman spectra from a bulk germanium sample it was found that the detectors were experiencing 0.27 to 0.48 % tensile strain, consistent with the enhanced absorption at extended wavelengths. Nanowire bridges were then fabricated in germanium and silicon-germanium and characterized using Raman spectroscopy. Germanium was found to have enhanced strain in the nanowire with an enhancement of up to 13.5 demonstrated, whereas for the silicon-germanium samples the structures were shown to reduce the compressive strain in the samples. It is concluded that strain engineering is a very promising route for the development of extended wavelength detectors integrated with silicon photonic systems. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24462 |
| Date | January 2019 |
| Creators | Anthony, Ross Edward |
| Contributors | Knights, Andrew, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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