Fig. 1. Preparation process of hyperdoped silicon and its photodetector. (a) Preparation of hyperdoped silicon by femtosecond-laser; (b) rapid thermal annealing to activate dopant elements; (c) preparation of aluminum electrode

Fig. 2. Doping characterizations of low-concentration hyperdoped silicon and high-concentration hyperdoped silicon. (a) Surface topography of low-concentration hyperdoped silicon by SEM test; (b) surface topography of high-concentration hyperdoped silicon by SEM test; (c) doping concentration distributions of two kinds of hyperdoped silicon

Fig. 3. Light intensity inverse-saturation phenomenon of high-concentration hyperdoped silicon photodetector and low-concentration hyperdoped silicon photodetector. (a) Photocurrent versus with light intensity for two kinds of hyperdoped silicon photodetectors; (b) schematic of refined defect-assisted photoconductive gain model

Fig. 4. Light intensity inverse-saturation of low-concentration hyperdoped silicon photodetector at different wavelengths with 2 V reverse bias. (a) Variations of photocurrent with wavelength for hyperdoped silicon photodetector at different light intensities; (b) variations of photocurrent with light intensity for hyperdoped silicon photodetector at different wavelengths

Fig. 5. Light intensity inverse-saturation of low-concentration hyperdoped silicon photodetector at different reverse biases. (a)‒(c) Variations of photocurrent with wavelength for hyperdoped silicon photodetector at different light intensities at 4, 7, and 8 V reverse biases; (d) variations of photocurrent with light intensity for hyperdoped silicon photodetector at different wavelengths at 7 V reverse bias

Fig. 6. Bias inverse-saturation of low-concentration hyperdoped silicon photodetector at 13.75 μW irradiated light intensity. (a) Variations of photocurrent with wavelength at different reverse biases (1‒7 V); (b) variations of photocurrent with wavelength at different reverse biases (7‒13 V)

Fig. 7. Schematic diagrams of bias inverse-saturation mechanism of low-concentration hyperdoped silicon photodetector. (a) Band variation of photodetector under different reverse biases; (b) bias inverse-saturation of photodetector at different wavelengths

Fig. 8. Variations of spectral responsivity of low-concentration hyperdoped silicon photodetector with irradiated light intensity at different reverse biases (comparison with commercial standard silicon photodetector under 10 V reverse bias)