Vertical Field-Effect Near-Infrared Phototransistor with High Responsivity and Detectivity Based on a Au Nanowire Porous Source and a Mixed PbSe-HfO2 Sensing Layer

Near-infrared (NIR) detection is essential for applications in optical communications, biomedical imaging, and environmental monitoring. However, conventional NIR photodiodes face inherent trade-offs between responsivity and noise, largely due to thermal excitation in narrow-bandgap materials often necessitating cryogenic cooling to achieve an acceptable performance. In this study, we demonstrate a vertical field-effect NIR phototransistor (VFEPT) that integrates a mixed lead selenide quantum dot (PbSeQD)–hafnium dioxide nanoparticle (HfO2 NP) sensing layer with a porous gold nanowire source, enabling significantly improved photodetection capabilities. The high permittivity of HfO2 facilitates substantial charge accumulation and modulates the Schottky junction, while its low electrical conductivity suppresses leakage current even in the presence of narrow-bandgap PbSeQDs. This synergistic configuration effectively reduces the dark current, minimizes noise, and enhances detectivity. Additionally, the large capacitance between the gate and the source boosts charge accumulation, resulting in an amplified photocurrent and enhanced responsivity. Under NIR illumination, PbSeQDs efficiently absorb photons and generate electron–hole pairs, reinforcing the gate–source electric field and further increasing charge accumulation, thereby yielding a substantial photocurrent gain while maintaining low noise levels. The proposed VFEPT achieves a high responsivity of 256 A W–1 and a detectivity of 2.5 × 1015 Jones at 1550 nm, outperforming conventional NIR photodiodes and demonstrating exceptional potential for low-noise, high-responsivity NIR detection.