High photosensitivity in amorphous silicon-capped silicon nanocrystals embedded in metal-insulator-semiconductor structures (Al/@Si/Si NCs/SiO₂/n-Si) for photodetection and energy harvesting

In this paper, we grow and integrate amorphous silicon-capped silicon nanocrystals (Si NCs) into a Metal-Insulator-Semiconductor (MIS) structure to enhance its performance in visible photodetection and energy harvesting. The studied Si NCs were fabricated by solid-state dewetting of an ultrathin amorphous silicon-on-insulator (a-SOI) film, yielding nanocrystals with remarkable morphological and structural properties. These Si NCs exhibit high density (5 × 1011/cm2), a well-defined hemispherical shape, a uniform size, and a single-crystal structure. Electrical measurements on these nanocrystals, capped with a 15 nm-thick amorphous silicon layer, show that this encapsulation enhances charge transport in the MIS structure. Current-voltage measurements, performed both in the dark and under visible illumination, reveal that the MIS structure integrating Si NCs capped with amorphous silicon is highly photosensitive, with a current increase of a factor of 300 under visible light excitation at a bias of VB = −1 V. This high photosensitivity is attributed to the synergistic contribution of the Si NCs and the amorphous silicon coating, which improves the electrical transport efficiency and promotes the photogeneration of electron-hole pairs. These results demonstrate that this novel strategy can lead to a significant improvement in the photosensitivity of MIS-based photodetectors.