Growth of Ge QDs-Decorated SiGe Nanocrystals: Toward Integration of Quantum Dots and Mie Resonators in Ultrathin Film for Photodetection and Energy Harvesting

To efficiently integrate SiGe-based Mie resonators and germanium quantum dots into a single-layer structure for ultrathin solar cells and high performance self-powered photodetectors, we introduce an innovative method involving solid-state dewetting and germanium (Ge) condensation within SiGe nanocrystals. This results in the growth of SiGe/SiO2-SiGe-SiO2 core/shells nanocrystals decorated with Ge quantum dots. The process begins with solid-state dewetting, initiating the growth of SiGe core nanocrystals (Mie resonators) from a Ge layer initially deposited via molecular beam epitaxy on an ultrathin silicon-on-insulator (UT-SOI) film. Subsequently, SiO2-SiGe-SiO2 shells form through thermal oxidation, encapsulating the SiGe nanocrystals by germanium condensation. Finally, Ge quantum dots are grown by molecular beam epitaxy (MBE), resulting in concentric core/multishell nanocrystals embellished with minuscule Ge quantum dots. Our original nanostructure, validated via HR-TEM and HAADF analysis, represents a significant breakthrough in the integration of both Ge QDs and SiGe Mie resonators in one ultrathin layer for optoelectronic applications. Remarkably, these engineered nanostructures demonstrate a photovoltaic effect in the visible spectrum. Anticipating significant potential, this distinctive configuration holds promise for fostering advancements in optoelectronics and sensing applications.