Fig. 1. Schematic of laser doping apparatus and the main doping related components: (i) 308 nm XeC1 pulsed excimer laser, (ii) homogenizing optics, (iii)x–y stage and gas cell, and (iv) SUN workstation. Also shown are the diagnostic related components: (i) HeNe laser, (ii) CCD camera and monitor, (iii) PIN photodetectors, and (iv) fast digitizing oscilloscope. Reproduced with permission from Ref. [55]. Copyright Elsevier 1989.

Fig. 2. (Color online) (a) Temperature-dependent PL spectra: Temperature-dependent peak amplitude at 1536 nm for DC- and RTA-processed Er/O-Si samples. Inset: the temperature-dependence of PL spectra for DC-processed samples. (b) Room-temperature PL spectra for DC-and RTA-processed samples. (c) Fast and slow decay times as a function of temperature for DC- and RTA-processed samples. Reproduced with permission from Ref. [79]. Copyright Wiley-VCH 2020.

Fig. 3. (Color online) Schematic illustration of sub-bandgap charge carrier excitation in deep-level impurity band (intermediate band) of hyperdoped Si.

Fig. 4. (Color online) (a) Absorptance spectra for S-, Se-, and Te-hyperdoped Si after annealing to 775 K for increasing lengths of time (from top to bottom: 10 min, 30 min, 100 min, 6 h, 24 h). (b) Normalized absorptance for S- (circles), Se- (squares), and Te- (triangles) hyperdoped Si after various thermal anneals versus diffusion length of the respective dopant. Reproduced with permission from Ref. [95]. Copyright Springer-Verlag 2009. (c) Schematic of the two-step annealing process that first deactivates the sub-bandgap absorptance by annealing at 1070 K and then reactivates it via one of two methods: high temperature 1510 K annealing and quenching or fs-pulsed laser irradiation. Reproduced with permission from Ref. [96]. Copyright AIP Publishing 2011.

Fig. 5. (Color online) (a) Side-view SEM image of the S-hyperdoped Si sample prepared using ns-laser pulses. (b) Light reflection spectra of ns-laser-fabricated S-hyperdoped Si samples before and after the thermal annealing. The top insets A and B are schematic diagrams, which illustrate the optical path of light incident on the surface of conical structures before and after the thermal annealing. (c) Light absorption spectra of the ns-laser-fabricated S-hyperdoped Si samples before and after the thermal annealing (different S-dopant diffusion lengths). Reproduced with permission from Ref. [97]. Copyright Elsevier 2017. SEM images of the Si (001) wafer surface (d) after chemical texturing and (e) after laser melting. (f) Absorptance spectra of the non-textured and textured hyperdoped silicon samples, along with the pristine silicon wafer. Reproduced with permission from Ref. [98]. Copyright Springer Nature 2015.

Fig. 6. (Color online) (a) Evolution of the Si nanocrystals band structure with the increase of the doping level of B. ABS: absorption onset;E_c: conduction band edge;E_v: valence band edge;E_f: Fermi energy level;E_a: impurity energy level. (b) Bandgap narrowing associated with the indirect transition (T₀) and direct transition (T₁) obtained in heavily B-doped Si nanocrystals. Reproduced with permission from Ref. [99]. Copyright American Chemical Society 2016.

Fig. 7. (Color online) (a) FTIR spectra of ~6.8 nm undoped and B-hyperdoped Si nanocrystals. (b) FTIR spectra of ~2.4, 3.8, and 6.8 nm B-hyperdoped Si nanocrystals with the B concentration of ~17%. (c) The peak positions of the LSPR-induced absorption that is fitted with dashed lines are indicated by dotted lines. Reproduced with permission from Ref. [102]. Copyright Wiley-VCH 2016. FTIR spectra of 14.6 at% B-hyperdoped Si nanocrystals with 600, 700, and 800 °C annealing temperatures. (d) FTIR spectra of the as-synthesized (solid lines) and one-year air-exposed (dashed lines) undoped and B-hyperdoped Si nanocrystals. Reproduced with permission from Ref. [103]. Copyright Wiley-VCH 2019.

Fig. 8. (Color online) (a) TEM image and (b, c) EDS element mapping of P-hyperdoped Si nanowires. (d) Two-probeI–V measurements of P-hyperdoped Si nanowires and intrinsic Si nanowires for comparison. Reproduced with permission from Ref. [111]. Copyright American Chemical Society 2021.

Fig. 9. (a) The sketch of the structure of Si–Ti–Si. (b) Atom concentration and the atom percentage of Ti in sample after PLM. (c) Light absorption coefficient of the thin film wafer of samples and Si. Reproduced with permission from Ref. [117]. Copyright Science Press 2018.

Fig. 10. (Color online) (a) Sample geometry of Si–S–Si multilayered films. (b) TEM bright-field images of Si–S–Si multilayered films after ns-pulsed laser irradiation with fluences of 175 mJ/cm². (c) Absorptance profiles of the S-hyperdoped Si samples and the substrate, temperature characteristics of (d) sheet carrier concentration, (e) Hall mobility and (f)sheet resistance for the S-hyperdoped Si samples and the substrate. Reproduced with permission from Ref. [119]. Copyright Elsevier 2019.

Fig. 11. (Color online) (a) Schematic representation of the recoil-Fe atom implantation method. (b) HRTEM image of the (110) cross section of the Si:Fe/p-Si structure. (c) DarkI–V characteristics of the p-Si substrate and the n-Si:Fe/p-Si diode structure and (d) photoresponse of the n-Si:Fe/p-Si sample at various values of the reverse bias (U = 0–1.6 V) and the commercial silicon photodiode FD-27K at the reverse biasU = 10 V. Reproduced with permission from Ref. [71]. Copyright Elsevier 2020.

Fig. 12. (Color online) (a) Cross-sectional structure of Si-photodiode based on microstructured Si. (b) Responsivity versus laser fluence at –5 V bias. (c) Responsivity versus etching time at –5 V bias. Reproduced with permission from Ref. [131]. Copyright IOP Publishing 2018.

Fig. 13. (Color online) (a–g) The spectral responsivity measured at zero bias (i.e., photovoltaic mode) for the Te-hyperdoped Si photodetector at different temperatures. (h) Brown short dot is the room-temperature spectral responsivity of a commercial Si-PIN photodiode (model: BPW34). Illustration of the below-bandgap photoresponse in the Te-hyperdoped Si photodetector. Process I: valence band to conduction band (E_ph ≥ E_g); Process II: valence band to intermediate band (E_ph ≥E_g –E_Te); Process III: intermediate band to conduction band (E_ph ≥E_Te, only measurable at low temperatures where the thermal contribution is neglected). Reproduced with permission from Ref. [135]. Copyright Wiley-VCH 2021.

Fig. 14. (Color online) (a) Au-hyperdoped Si-based photodiode with Si:Au layer on n-Si substrate operating at reverse bias. (b) DarkI–V curves of three different Au implantation doses. (c) Difference between dark and illuminatedI–V of the photodiode with 10¹⁵ cm^–2 Au dose. (d) Mapped EQE of Si:Au layer for 1550 nm. (e) Mapped EQE of Si reference for 1550 nm. (f) EQE of Au-hyperdoped Si-based photodiode for three different sub-band gap wavelengths. Reproduced with permission from Ref. [27]. Copyright nature publishing group 2014.

Fig. 15. (Color online) Schematic cross-section of Si-based solar cell structures. S-hyperdoped Si layer directly grown on the (a) back surface and (b) front surface of solar cell. Reproduced with permission from Ref. [119]. Copyright Elsevier 2019.

Fig. 16. (Color online) (a) Deduced contact resistance vs. B doping concentration. (b) Resistance vs. temperature for a superconductor junction. The bias lock-in current is 5 nA. The contacts transition temperature can be seen at 215 mK, while the weak link transits is at a lower temperature (~160 mK). On the right, schematics of the resistance jumps origin. Inset: current-voltage characteristic atT = 80 mK. Reproduced with permission from Ref. [123]. Copyright Elsevier 2014.

Fig. 17. (Color online) (a) Schematic illustration of the gas sensor. (b) Gas responses to various gases or volatile organic compound vapors and (c) response time and recovery time of the gas sensor upon the exposure to 20 ppm NO₂ gas with different storage days. Reproduced with permission from Ref. [147]. Copyright Elsevier 2022.

Table 1. The performance of photodetectors based on hyperdoped Si.