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What is a Silicon Photodetector?

A silicon photodetector is a device that is used to detect light and convert it into an electrical signal. Silicon photodetectors are made from silicon, which is a semiconductor material that has intermediate electrical conductivity between that of a conductor and an insulator.

Silicon photodetectors operate by converting the energy of light into electrical charges, which can be measured and amplified to produce an electrical signal. When light is absorbed by a silicon photodetector, it generates electron-hole pairs in the silicon, which are then separated and collected by electrodes on the device. The resulting current is proportional to the intensity of the light, and it can be used to detect and measure light levels.

Silicon photodetectors are used in a wide range of applications, including imaging, sensing, and communication systems. They are widely used in consumer electronics, such as smartphones and digital cameras, as well as in scientific and industrial applications. Silicon photodetectors have a number of advantages over other types of photodetectors, including high sensitivity, fast response time, and low cost.

Overall, silicon photodetectors are an important component in many electronic systems, and they play a crucial role in enabling the detection and measurement of light levels in a variety of applications.

silicon photodetector diagram

Silicon photodetectors are devices used for detecting light in the infrared and microwave frequency ranges. There are many different types and they have a wide array of characteristics, such as the size, bandwidth, and structure.


Silicon Photodetectors are used in a wide range of applications. They are essential for video imaging, biomedical imaging, night vision, gas sensing and many other applications. In addition, they are necessary for security purposes. The market for silicon photodetectors is projected to increase in the coming years. It is estimated that the global market for this product will reach million USD in 2028.

Silicon-on-insulator (SOI) substrates have been used in many applications. They have allowed for high-speed modulators, optically pumped lasers and reliable CMOS-compatible optical components. In addition, they have provided for improved optical coupling efficiency.

There are several manufacturing processes used to produce photodetectors. One of the common approaches is the deposition of a thin metallization on the silicon wafer. This can be done by sputtering or by evaporation. Typically, the metal electrodes are annealed after deposition.

In addition to sputtering, another method is the use of evaporation to deposit the metal electrodes on the silicon. This procedure is commonly used for III-V-based devices. In this process, the morphology of the deposited film depends on the evaporation conditions. The resultant electrodes can be conductive, or they can be transparent.

For a photodetector to operate efficiently, the device must incorporate means to couple optical signals. The optical coupling efficiency can be improved by minimizing the parasitic electrical interconnections within the photodetector. However, this increases thermal noise, bandwidth and resistance.

To overcome these limitations, integrated photodetectors have been developed. These devices can be used for wavelength division multiplexing (WDM) and combine the L and C band. In addition, they can be combined with dense wavelength division multiplexing to achieve a bandwidth of 0.5 THz or higher.

The performance of a photodetector depends on the semiconductor bandgap structure and the device's responsivity. The maximum responsivity achieved with an optimized integrated photodetector is 64 mA/W at 1,440 nm.


Infrared silicon photodetectors are an essential component of electronics. Infrared sensors have become increasingly important in the telecommunication industry, where components must operate in this range. As technology progresses, the need for bandwidth increases at 5 GHz. Therefore, the development of high-performance waveguide-integrated photodetectors has remained a vital task. This chapter discusses the most important results that have been obtained in the past few years.

Infrared silicon photodetectors can be easily fabricated. They can measure the wavelengths in the range from 1.2 to 2.1 mm. This makes them useful in autocorrelation for measuring ultra-short laser pulses. They also offer a large in-plane charge WS2 carrier mobility and a fast photoresponse speed. In addition, they can establish a connection between electronics and photonics.

A typical silicon photodetector can be made with a single 1 V applied bias and a dark current of less than a mA. The resulting device is a p-i-n diode, which is embedded in a silicon waveguide. Its transverse cross section is about 0.5 mm, while its radius is 40 mm. A corresponding finesse value is 4.7.

A wide range of physical effects are involved in the absorption of light in silicon. They include two-photon absorption, internal photoemission, and surface-state absorption. These effects influence the conductivity of the device. They also allow for the measurement of impurities. These measurements can be performed on bulk materials, Schottky junctions, and p-n junctions.

In order to achieve a high-performance silicon-based infrared photodetector, the effect of extrinsic generation must be addressed. Schottky barriers are used to increase the collection efficiency of the barrier. They can be fabricated using a nickel silicide layer on a silicon substrate. Alternatively, a Cu/p-Si Schottky barrier can be used for higher performance and operation in the gigahertz range.


Silicon photodetectors have excellent performance in the 850 nm band. Moreover, these detectors offer high responsivity, which ensures a low detection noise and a high signal-to-noise ratio. They also have applications in terahertz generation, neuromorphic computing, and high-speed signal processing. However, they have limited bandwidth due to the low capacitance and resistance. Therefore, they are ideal for short-distance optical communication.

Si photodetectors can be incorporated in a waveguide. In this case, the optical field will be coupled into the resonant cavity of the photodetector. The resonant cavity enhances the photodetector's response and overcomes the lack of absorption in the silicon substrate.

Another type of ring-coupled silicon MSM (MSM) photodetector is an RCPD. This device comprises a race-track SiN ring resonator and a silicon MSM photodetector. Compared with the typical Si photodetector, the RCPD offers a higher gain-product and better transmission speed.

The bandwidth of the RCPD depends on the gap and the length of the interaction between the resonator and the bus of the photodetector. The length of the interaction is measured from the I-V characteristics of the photodetector. The device is designed to operate in the single-mode 850 nm region. The theoretical depletion length is 1.7 m.

In contrast, a conventional silicon technology can be used to achieve comparable performance. Unlike InP-based photodetectors, the silicon photodetector does not need cumbersome III-V material transfer. It can be fabricated on a silicon-on-insulator (SOI) or epitaxial substrate.

In addition to the advantages of conventional silicon technology, a novel germanium photodetector can be employed. It can be used for free-space optical communication and for ultrafast spectroscopy. It has an internal responsivity of 0.45 A W-1 at 240 GHz. Moreover, its depletion capacitance can be reduced from 9.5 fF at zero bias to 6.5 fF at -2 V.


Silicon photodetectors have been widely used for many important applications. Especially, they have been applied for optical computing, lab-on-chip sensor, and laser radar. To meet the demand of low-cost, high-performance photodetection, researchers have developed various structures for silicon photodetectors. Here, we will briefly discuss the recent progress of two-dimensional materials (IPE)-based silicon photodetectors at near-infrared wavelengths.

IPE-based silicon photodetectors include G-Si heterostructure and waveguide-integrated 2DM PDs. The two-dimensional material possesses excellent performance in ultrabroad operation wavelength ranges. The waveguide-integrated 2DM PDs have attracted much attention in recent years. These PDs have potential applications in various functional photonic integrated circuits.

The G-Si heterostructure is one of the most widely-used configurations for PDs. It has a high position sensitivity and low response nonlinearity in the NIR region. This is because of the presence of an interface-trapped charge located at the Si-SiO2 interface. This charge is formed by structural defects and bond-breaking processes in the oxide layer. The oxidation process can also be responsible for this charge.

A new structure has been manufactured for photonic crystal nanocavity photodetectors. The structure consists of a trench deposited on a thick layer of silicon oxide. A Cu film is then placed on the bottom of the trench. The Cu film provides a large surface area for electrical pad contact. This structure has the potential to be used for integrating photodetectors in complex microcavities. It can improve the finesse of the photodetector.

A waveguide-integrated silicon-2DM PD has attracted considerable attention. The device is capable of suppressing noise, lowering resistance, and improving responsivity. Its optimum room temperature specific detectivity is 2x 109 Jones at 1.7 mm. Moreover, the responsivity is comparable to that of metal-2DM-metal PDs.


Silicon photodetectors are physical devices that are used for accurate measurement of light intensity and lighting regulation. They are commonly used in medical equipment and imaging applications. They are also used in instruments to analyze samples. They can be designed and manufactured in low-cost, standard silicon processing technology.

Typical photodetector operating voltage is around 5 V. However, the voltage may be higher when amplifier noise is more intense than the photodetector's noise. In this case, a bias voltage of 1 V is a feasible choice.

The silicon band gap is 1.14 eV. This energy difference is located between the conduction band and the valence band of silicon. The energy of an E-field must exceed this energy to create avalanche photons.

There are two types of photoconductivity effects: internal photoemission absorption and surface state absorption. In the case of internal photoemission absorption, an electron-hole pair is generated in the P-region. Shorter light wavelengths have shallower absorption depths in silicon. On the other hand, longer light wavelengths have higher absorption depths.

The avalanche process is the result of an increase in the population of carriers. During the process, carriers travel from the N (cathode) region to the P (anode) region. These carriers are sufficiently energetic to create holes that enter the valance band.

The number of holes and electrons in the valance band varies depending on the light source. In the case of longer wavelengths, more holes are formed, while in the case of shorter wavelengths, more electrons are formed. The length of the depletion layer determines the frequency response and the photosensitivity of the structure. In this way, increasing the width of the depletion layer increases the number of e-h pairs generated.

Video: What is a Photodetector?