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.