Hexagonal Ge on Self-assisted GaAs Nanowires by MBE

The increasing demand for data requires photonic technologies to overcome the limitations of traditional electronic interconnects. Silicon photonics offers a solution, but the integration of efficient light sources remains challenging due to silicon’s indirect bandgap. Germanium (Ge), though also indirect in its cubic phase, can achieve a direct bandgap in its hexagonal phase (h-Ge), making it a promising candidate for light emission. This thesis focuses on growing h-Ge on self-assisted GaAs nanowires (NWs) using molecular beam epitaxy (MBE). Optimized growth of GaAs NWs in the Wurtzite (WZ) phase enables high-quality h-Ge deposition. Structural and optical characterization confirm the presence of hexagonal Ge and demonstrate tunable light emission via quantum confinement, moving closer to telecommunication wavelengths. Challenges such as defects and contamination are discussed. This thesis highlights the potential of h-Ge for next-generation photonic devices.