Hexagonal SiGe Laser on silicon substrate
Researchers
Research Areas
Physics, Material Science, Photonics, Nanomaterials Synthesis and Applications, Laser, Catalysis, CO2 reduction, RWGS reaction
Project Brief
The “Hexagonal SiGe for Photonics” project addresses a critical challenge in silicon photonics: the lack of an efficient monolithic light source compatible with CMOS technology due to silicon’s indirect bandgap. In indirect bandgap materials like cubic Si, electron-hole recombination requires phonon assistance, making light emission inefficient. By contrast, direct bandgap materials enable efficient photon emission, as their valence band maximum and conduction band minimum align in momentum space.
This project leverages the unique properties of Hexagonal SiGe alloys, which exhibit direct bandgap behavior, as recently demonstrated experimentally (Fadaly et al., Nature 2020). The goal is to develop a hexagonal SiGe-based laser grown on silicon substrates, enabling integration with existing semiconductor technologies. The research comprises three key phases:
1. Material Growth and Characterization: Hexagonal SiGe will be epitaxially grown on III-V nanowires with wurtzite crystal structure, forming a core-shell geometry. Molecular beam epitaxy (MBE) will be used for precise control over composition and defects. Material quality will be verified via TEM, XRD, and photoluminescence to confirm the hexagonal phase and direct bandgap properties.
2. Device Fabrication: The project will design and fabricate laser cavities using cleanroom processes, including electron-beam lithography to pattern plasmonic structures or nanowire arrays that enhance light-matter interaction. Doping optimization will be critical for achieving efficient carrier injection.
3. Optical Characterization: The performance of laser will be evaluated by measuring threshold current, spectral linewidth, and output power under optical pumping. Success would mark a breakthrough in silicon-compatible light sources for applications in optical interconnects, sensing, and quantum technologies.
The project benefits from collaborations with INL (EC Lyon) for material growth and RMIT for device fabrication, with industrial partner LETI ensuring translational potential. By combining expertise in epitaxy, nanofabrication, and photonics, this work could enable next generation integrated photonic circuits.