Fig. 1. Device structure and working mechanism of the photo-FinFET. (a) A schematic illustration of the PbS-Si photo-FinFET. Infrared light “switches on” the PbS gate, allowing current to flow through the Si channel. (b) Energy band simulation results along the vertical direction of the Si channel. Inset: an enlarged view of the light green box, in which a schematic diagram of the dynamic process of photogenerated carriers under infrared illumination is depicted. (c) Simulated optical generation in the photo-FinFET under excitation by 1550 nm light. (d, e) Simulated electron (majority carriers) density in the photo-FinFET under darkness and 1550 nm illumination, respectively. (f) Electron density extracted along the dash-dotted lines in (d) and (e). (g) Conduction band energy extracted along the Si channel, i.e., the direction indicated by circles and dots in (d) and (e).

Fig. 2. Visible photoresponse and modulation characteristic of the photo-FinFET. (a) Transfer characteristic curves of the photo-FinFET under 635 nm illumination with varying power densities. (b) Top panel: transfer characteristic curve of the photo-FinFET in the dark state. Bottom panel: schematic diagrams of the carrier dynamics process in the channel of the photo-FinFET when it is in the depletion region and working region, respectively. (c) Output characteristic curves of the photo-FinFET under 635 nm illumination with different power densities. (d) Photocurrent and responsivity as a function of light power density.

Fig. 3. Infrared phototresponse of the photo-FinFET. (a, b) I-T curves of the photo-FinFET in response to 1550 nm and 2700 nm illumination under different V_bg. The power densities of the 1550 nm and 2700 nm illumination are 603.13 mW/cm² and 87.04 mW/cm², respectively. (c, d) Responsivity of the photo-FinFET as a function of the light power density under different V_bg. The wavelengths of the light sources are 1550 nm and 2700 nm, respectively.

Fig. 4. Response speed, noise and performance summary of the photo-FinFET. (a) Output signal of the photo-FinFET as a function of time under 1550 nm illumination. (b, c) Enlarged views of the rising and falling edges (indicated by the shaded boxed regions in (a)). (d) 3 dB bandwidth measurement results of the photo-FinFET under 635 nm and 1550 nm illumination. (e) Rising and falling times of the photo-FinFET at different V_bg. (f) Noise current of the photo-FinFET at different V_bg. (g) Measured noise current and calculated shot noise of the photo-FinFET. The calculation formula of shot noise is 2qI_dark, where q is the elemental charge and I_dark is the dark current. (h, i) Performance comparison of the photo-FinFET with previously reported Si-based photodetectors. The responsivity and NEP of the photo-FinFET presented in (h) and (i) are measured at V_bg = 50 V and V_bg = 30 V, respectively. These previously reported Si-based photodetectors are based on different strategies to enable infrared photodetection including, integrating infrared-absorbing materials (red icons), utilizing internal photoemission effect (orange icons), manufacturing black Si (green icons), exploiting intrinsic light absorption of Si (blue icons), and hyper-doping Si (purple icons). Parameters of the photo-FinFET are indicated by black icons.