Fig. 1. (a) Surface modification and hyperdoping system for preparing flat FSH silicon. HWP, half-wave plate; GTP, Glan-Taylor polarizer. (b) Structure of a flat FSH silicon photodetector. (c) Schematic diagram of flat FSH silicon used in CMOS processes.

Fig. 2. Morphologies and doping concentrations of flat FSH silicon and structured FSH silicon. (a) SEM image of flat FSH silicon. (b) SEM image of structured FSH silicon. (c) AFM analysis comparing the structural dimensions of flat FSH silicon and structured FSH silicon. (d) Graph of the sulfur concentration in flat FSH silicon.

Fig. 3. Characterization and comparison of doping effects on flat and structured FSH silicon. (a) Raman spectra of the silicon substrate, flat FSH silicon, and structured FSH silicon. (b) Absorption spectra of the silicon substrate, flat FSH silicon, and structured FSH silicon.

Fig. 4. Key performance indicators of the flat FSH silicon photodetector. (a) Spectral responsivity of the flat FSH silicon photodetector under a 5 V reverse bias, compared with a commercial Si photodetector, a structural Ge photodetector, and the 100% external quantum efficiency (EQE) reference line. (b) Specific detectivity under a 5 V reverse bias and the dark current of a flat FSH silicon photodetector.

Fig. 5. Experimental design for finding the mechanism of the gain in flat fs-laser sulfur-hyperdoped silicon photodetectors. (a) Test system for measuring the photocurrents in the FSHSi circuit and FSHSi-Si lateral junction circuit. (b) Photocurrents of the FSHSi circuit and FSHSi-Si lateral junction circuit under a 10 V reverse bias.

Fig. 6. Anti-saturation photodetection phenomena and theoretical explanations of flat fs-laser sulfur-hyperdoped silicon photodetectors. (a) Relationship between the photocurrent and irradiated light intensity. (b) Changes in the energy levels of a flat FSH photodetector as the irradiated light intensity varies.