A visible light enhanced Ti ₃ C ₂ T _x /silicon nanowire array heterojunction broadband photodetector based on leaky mode resonance

Silicon-based broadband photodetectors (BBPDs) are extensively utilized in both the civilian and military fields due to their advanced fabrication processes and superior optoelectronic properties. However, most silicon-based BBPDs exhibit significantly reduced response in the visible range compared to the near-infrared band, which limits their further application in advanced optoelectronic systems. In this study, a visible-light-enhanced Ti₃C₂T_x MXene/Si NW heterojunction BBPD is constructed by employing a small diameter silicon nanowire (Si NW) array. Ti₃C₂T_x MXene exhibits unique electrical and optical properties, especially high conductivity and transparency, which significantly enhance the optoelectronic performance of the device. Device analysis revealed that the photoresponse of the device in the visible light band increases as the diameter of Si NWs gradually decreases from 200 nm to 100 nm. Furthermore, the device with a Si NW diameter of 120 nm achieves a responsivity of ∼520 mA W^-1 under 660 nm illumination, comparable to that in the near-infrared band (532 mA W^-1 at 910 nm). Theoretical simulations suggest that this unique photoelectric characteristic is linked to leaky mode resonances (LMRs) in small-diameter Si NWs. These results demonstrate that small diameter Si NWs are potential building blocks for low-cost and high-performance silicon-based BBPDs in the future.