Silicon Doping Techniques for Advanced Photodetector Applications

Silicon, as the backbone of modern electronics, has long been limited by its indirect bandgap and equilibrium solubility limits for dopants. To extend its photoresponse into the short‐ and mid‐infrared regimes, researchers have developed non-equilibrium doping methods that introduce deep‐level impurities at concentrations far above thermal equilibrium. These approaches—including ion implantation followed by ultra-rapid annealing, femtosecond-laser hyperdoping, flash-lamp annealing and solid- or liquid-phase epitaxy—enable the formation of intermediate energy bands or impurity levels within the silicon bandgap. Such bands facilitate sub-band-gap absorption, allowing photons with energies below 1.12 eV to be detected. Recent advances have focused on achieving uniform dopant incorporation, minimising crystal defects, engineering Schottky barriers and optimising contact resistivity for high responsivity and low noise. Through careful control of annealing parameters, substrate temperature and dopant species, practical CMOS‐compatible photodetectors have been realised with room-temperature operation up to wavelengths of 5 µm. These developments promise the integration of broadband infrared sensing into cost-effective, silicon-based photonic platforms for applications in communications, environmental monitoring and biomedical imaging.

Research from Nature Portfolio

Recent studies have demonstrated that non-equilibrium Se hyperdoping yields room-temperature short-wavelength infrared photodiodes. By implanting selenium to concentrations approaching 10^21 cm^−3 followed by millisecond flash-lamp annealing, researchers have realised single-crystalline p-n junctions exhibiting strong sub-band-gap absorption and photoconductive gain at wavelengths around 1.3 µm. Complementary work on sulfur hyperdoped silicon has employed synchrotron-based spectroscopies and first-principles modelling to correlate chemical states of S dopants with the formation of impurity bands and insulator-to-metal transitions. These investigations reveal that monosulfide species dominate sub-band-gap absorption while annealing-induced clustering reduces detector sensitivity. Together, these findings elucidate the atomic and electronic origins of infrared response in hyperdoped silicon and guide optimisation of dopant chemistry and thermal processing.

Silicon Doping Techniques for Advanced Photodetector Applications publication trend

The graph below shows the total number of articles in silicon doping techniques for advanced photodetector applications across all publications each year (not limited to Nature Index journals).

Technical terms

Hyperdoping: Introduction of impurity concentrations into silicon far above thermal equilibrium to form deep-level or intermediate bands within the bandgap.

Sub-band-gap absorption: Optical absorption of photons whose energy is lower than the intrinsic bandgap of silicon, enabled by impurity or defect states.

Intermediate band: A partially filled energy band introduced within the semiconductor bandgap that permits two-step photon absorption processes.

Flash-lamp annealing (FLA): A millisecond-scale thermal treatment using intense light pulses to activate dopants and recrystallise damaged layers without bulk heating.

Specific detectivity (D*): A figure of merit for photodetectors, normalised to detector area and bandwidth, indicating sensitivity to weak optical signals.

References

1. Achieving ultralow contact resistivity in Si via Te hyperdoping and millisecond post-metallization annealing. Acta Materialia (2024).
2. Room-temperature short-wavelength infrared Si photodetector. Scientific Reports (2017).
3. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy. Scientific Reports (2015).
4. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques. Scientific Reports (2015).
5. Room‐Temperature Infrared Photoresponse from Ion Beam–Hyperdoped Silicon. physica status solidi (a) – applications and materials science (2020).
6. Highly responsive tellurium-hyperdoped black silicon photodiode with single-crystalline and uniform surface microstructure.. Optics Express (2020).
7. Toward understanding and optimizing Au-hyperdoped Si infrared photodetectors. APL Materials (2020).