High-Detectivity UV-Sensitive 2D MoS₂ Phototransistors Enhanced by Silicon Quantum Dots

Two-dimensional (2D) semiconductors have recently attracted tremendous interest as phototransistors due to their unique optical and electronic properties. However, for monolayer phototransistors, the detectable spectral range and the light absorption efficiency are usually quite limited. Here, we demonstrate phototransistors based on a van der Waals heterostructure (vdWH) formed by zero-dimensional (0D) silicon quantum dots (SiQDs) and 2D molybdenum disulfide (MoS₂), which show high detectivity and responsivity, especially in the ultraviolet (UV) spectral range. Compared to the phototransistor based on monolayer MoS₂ alone, the SiQD/monolayer MoS₂ vdWH phototransistor exhibits 100 times improvement in detectivity (from 1.0 × 10¹² to 1.0 × 10¹⁴ cm × Hz^1/2/W) and 89 times improvement in responsivity (from 66.7 to 6.0 × 10³ A/W) at 365 nm. The enhanced detectivity and responsivity are also observed for SiQD/a few-layer MoS₂ vdWHs. Analysis and control experiments show that charge transfer across the SiQD/MoS₂ vdWH leads to a photogating effect and photogain. The high-performance SiQD/MoS₂ vdWH phototransistors hold great promise for ultrasensitive photodetection, UV-based optical communication, neuromorphic visual sensing, and in-sensor computing applications.