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| intro_cmos [2026/05/19 14:58] – [Photodetector principle] antoine | intro_cmos [2026/05/19 16:09] (current) – [CMOS vertical photodiiodes types] antoine |
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| //Silicon photodetectors can create photogenerated currents for impinging light with wavelengths across the complete visible range. The produced photocurrent is proportional to the intensity of the incident light and is given by : | //Silicon photodetectors can create photogenerated currents for impinging light with wavelengths across the complete visible range. The produced photocurrent is proportional to the intensity of the incident light and is given by : |
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| $$I_{ph} = \frac{e \times QE \times \lambda \times P_i}{hc} = \frac{e \times QE \times P_i}{hv} \hfill (1)$$ | $$I_{ph} = \frac{e \times QE \times \lambda \times P_i}{hc} = \frac{e \times QE \times P_i}{hv} $$ |
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| //where I<sub>ph</sub> [A] is the photocurrent, e [C] is the elementary charge, λ [m] is the wavelength of the incident light, QE [%] is the quantum efficiency, P<sub>i</sub>[W] is the incident optical power, h [J.Hz<sup>−1</sup>] is Plank’s constant, and c [m.s<sup>−1</sup>] is the velocity of light in a vacuum. The quantity $E = \frac{hc}{\lambda} = h\nu$[eV] is the energy of a photon and ν [Hz] is the frequency of the photons. Formally, the quantum efficiency is determined by the ratio of the generated electrons N<sub>e</sub> to the incident photons N<sub>ph</sub> within the photodetector :// | //where I<sub>ph</sub> [A] is the photocurrent, e [C] is the elementary charge, λ [m] is the wavelength of the incident light, QE [%] is the quantum efficiency, P<sub>i</sub>[W] is the incident optical power, h [J.Hz<sup>−1</sup>] is Plank’s constant, and c [m.s<sup>−1</sup>] is the velocity of light in a vacuum. The quantity $E = \frac{hc}{\lambda} = h\nu$[eV] is the energy of a photon and ν [Hz] is the frequency of the photons. Formally, the quantum efficiency is determined by the ratio of the generated electrons N<sub>e</sub> to the incident photons N<sub>ph</sub> within the photodetector :// |
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| {{ ::3_types_of_photodiiode_structure_and_1_phototransistor.png?direct&600 |https://www.mdpi.com/2079-9292/13/4/691#metrics}} | {{ ::3_types_of_photodiiode_structure_and_1_phototransistor.png?direct&600 |https://www.mdpi.com/2079-9292/13/4/691#metrics}} |
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| | The best type of junction depends on the CMOS structure [([[https://www.mdpi.com/2079-9292/13/4/691 | Gounella, R.; Ferreira, G.M.; Amorim, M.L.M.; Soares, J.N., Jr.; Carmo, J.P. A Review of Optical Sensors in CMOS. Electronics 2024, 13, 691. https://doi.org/10.3390/electronics13040691]])] : |
| | * for 0.7 $\mu$m CMOS process : N<sup>+</sup>/P-sub |
| | * for 0.35 $\mu$m CMOS process : N-well/P-sub |
| | * for 0.18 $\mu$m CMOS process : P<sup>+</sup>/N-well |
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