Design and performance of SbSI/MoTe2 heterojunction photodetectors: Balancing low dark current with high responsivity

This study addresses the challenge of balancing key performance parameters in high-performance photodetectors, such as responsivity, dark current, and spectral response range. SbSI, a V–VI–VII group ternary compound, has shown promise for photodetection due to its narrow bandgap and high light absorption, but its single-component photodetectors suffer from high dark current, limited spectral range, and low carrier separation efficiency. Using first-principles density functional theory calculations, the study predicts the feasibility of constructing van der Waals (vdW) heterojunctions between SbSI and MoTe2. A mixed-dimensional vdW heterojunction photodetector was fabricated, combining exfoliated SbSI microrods and MoTe2. Experimental results demonstrate that this heterojunction device outperforms single-component SbSI devices: under a 5 V bias, the dark current is reduced to below 5 pA, photoresponsivity is doubled (maximum 39 mA/W), and the spectral response range is extended to 800 nm, covering the visible to near-infrared spectrum. The enhanced performance is primarily attributed to the interfacial band bending, built-in potential barrier, and charge redistribution induced by the SbSI/MoTe2 heterojunction, which effectively suppress dark current carrier transport while maintaining efficient photocarrier extraction under illumination. This work provides important theoretical and technical insights into the design of high-performance photodetectors based on V–VI–VII group compounds. The straightforward device fabrication process and improved performance make it a promising candidate for large-scale integrated applications, offering significant potential in various optoelectronic fields.