Photocurrent and electrical properties of SiGe nanocrystals grown on insulator via solid-state dewetting of Ge/SOI for Photodetection and solar cells applications

In this study, we present the photocurrent and electrical characterization of silicon-germanium nanocrystals (SiGe NCs) on an insulator (SiO₂). The SiGe NCs were grown through a hybrid process combining solid-phase dewetting of an ultra-thin silicon-on-insulator (UT-SOI) film with the epitaxial deposition of a thin germanium layer using ultra-high vacuum molecular beam epitaxy (UHV-MBE). These SiGe NCs were successfully integrated into the insulator layer of a metal-insulator-semiconductor (MIS) structure for optoelectronic applications. The enhanced MIS structure, featuring integrated SiGe NCs, exhibited notable transport and optoelectric properties as determined by current-voltage and impedance spectroscopy. The results indicated that the MIS structure functions as a Schottky diode, demonstrating a high rectification ratio (RR) of approximately 1000 and a Schottky barrier height (ϕ_B) of 0.73 eV. Additionally, this structure displayed a broad spectral response in the visible range, with a significant photovoltaic effect. The equivalent circuit of the MIS structure was also derived for an AC signal using impedance spectroscopy. These findings offer a promising scalable method for the monolithic integration and efficient growth of SiGe nanocrystals, paving the way for advancements in self-powered photodetectors and ultrathin solar cells.