Photodetectors Devices Circuits And Applications PdfBy Gustave B. In and pdf 16.05.2021 at 19:45 6 min read
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Fundamentals of Solid State Engineering pp Cite as. In this Chapter, we hAve explored the topic of photon detectors. In particular, photoconductive and photovoltaic detector types were discussed in detail. Specific photodetector examples were also described, including p-i-n, avalanche, Schottky barrier, metal-semiconductor-metal, type I1 superlattice, and photoelectromagnetic detectors, as well as quantum well and quantum dot photodetectors.
A junction photodiode is an intrinsic device that behaves similarly to an ordinary signal diode, but it generates a photocurrent when light is absorbed in the depleted region of the junction semiconductor. A photodiode is a fast, highly linear device that exhibits high quantum efficiency based upon the application and may be used in a variety of different applications.
It is necessary to be able to correctly determine the level of the output current to expect and the responsivity based upon the incident light.
Depicted in Figure 1 is a junction photodiode model with basic discrete components to help visualize the main characteristics and gain a better understanding of the operation of Thorlabs' photodiodes. Figure 1: Photodiode Model. Responsivity The responsivity of a photodiode can be defined as a ratio of generated photocurrent I PD to the incident light power P at a given wavelength:.
Modes of Operation Photoconductive vs. Photovoltaic A photodiode can be operated in one of two modes: photoconductive reverse bias or photovoltaic zero-bias. Mode selection depends upon the application's speed requirements and the amount of tolerable dark current leakage current.
Photoconductive In photoconductive mode, an external reverse bias is applied, which is the basis for our DET series detectors. The current measured through the circuit indicates illumination of the device; the measured output current is linearly proportional to the input optical power. Applying a reverse bias increases the width of the depletion junction producing an increased responsivity with a decrease in junction capacitance and produces a very linear response.
Operating under these conditions does tend to produce a larger dark current, but this can be limited based upon the photodiode material. Note: Our DET detectors are reverse biased and cannot be operated under a forward bias. Photovoltaic In photovoltaic mode the photodiode is zero biased. The flow of current out of the device is restricted and a voltage builds up. This mode of operation exploits the photovoltaic effect, which is the basis for solar cells. The amount of dark current is kept at a minimum when operating in photovoltaic mode.
Dark Current Dark current is leakage current that flows when a bias voltage is applied to a photodiode. When operating in a photoconductive mode, there tends to be a higher dark current that varies directly with temperature.
Of course, applying a higher bias will decrease the junction capacitance but will increase the amount of dark current present. The dark current present is also affected by the photodiode material and the size of the active area. Silicon devices generally produce low dark current compared to germanium devices which have high dark currents. The table below lists several photodiode materials and their relative dark currents, speeds, sensitivity, and costs. Junction Capacitance Junction capacitance C j is an important property of a photodiode as this can have a profound impact on the photodiode's bandwidth and response.
It should be noted that larger diode areas encompass a greater junction volume with increased charge capacity. In a reverse bias application, the depletion width of the junction is increased, thus effectively reducing the junction capacitance and increasing the response speed.
Bandwidth and Response A load resistor will react with the photodetector junction capacitance to limit the bandwidth.
This is useful, as the NEP determines the ability of the detector to detect low level light. In general, the NEP increases with the active area of the detector and is given by the following equation:. Terminating Resistance A load resistance is used to convert the generated photocurrent into a voltage V OUT for viewing on an oscilloscope:. Depending on the type of the photodiode, load resistance can affect the response speed.
This will minimize ringing by matching the cable with its characteristic impedance. If bandwidth is not important, you may increase the amount of voltage for a given light level by increasing R LOAD. In an unmatched termination, the length of the coaxial cable can have a profound impact on the response, so it is recommended to keep the cable as short as possible.
Shunt Resistance Shunt resistance represents the resistance of the zero-biased photodiode junction. This can significantly impact the noise current on the photodiode. For most applications, however, the high resistance produces little effect and can be ignored.
Series Resistance Series resistance is the resistance of the semiconductor material, and this low resistance can generally be ignored.
The series resistance arises from the contacts and the wire bonds of the photodiode and is used to mainly determine the linearity of the photodiode under zero bias conditions. The DET series detectors are modeled with the circuit depicted above. The detector is reverse biased to produce a linear response to the applied input light. The amount of photocurrent generated is based upon the incident light and wavelength and can be viewed on an oscilloscope by attaching a load resistance on the output.
The function of the RC filter is to filter any high-frequency noise from the input supply that may contribute to a noisy output. Figure 3: Amplified Detector Circuit.
One can also use a photodetector with an amplifier for the purpose of achieving high gain. The user can choose whether to operate in Photovoltaic of Photoconductive modes. There are a few benefits of choosing this active circuit:. The photoconductor signal will remain constant up to the time constant response limit.
The detector will exhibit lower responsivity at lower chopping frequencies. Frequency response and detectivity are maximized for. Schliessen [X]. All Optical Tutorials on Thorlabs. Photodiode Tutorial Photodiode Tutorial Theory of Operation A junction photodiode is an intrinsic device that behaves similarly to an ordinary signal diode, but it generates a photocurrent when light is absorbed in the depleted region of the junction semiconductor. Figure 1: Photodiode Model Photodiode Terminology Responsivity The responsivity of a photodiode can be defined as a ratio of generated photocurrent I PD to the incident light power P at a given wavelength: Modes of Operation Photoconductive vs.
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Photodetectors Devices, Circuits and Applications
A junction photodiode is an intrinsic device that behaves similarly to an ordinary signal diode, but it generates a photocurrent when light is absorbed in the depleted region of the junction semiconductor. A photodiode is a fast, highly linear device that exhibits high quantum efficiency based upon the application and may be used in a variety of different applications. It is necessary to be able to correctly determine the level of the output current to expect and the responsivity based upon the incident light. Depicted in Figure 1 is a junction photodiode model with basic discrete components to help visualize the main characteristics and gain a better understanding of the operation of Thorlabs' photodiodes. Figure 1: Photodiode Model.
Photodetectors: Materials, Devices and Applications discusses the devices that convert light to electrical signals, key components in communication, computation, and imaging systems. In recent years, there has been significant improvement in photodetector performance, and this important book reviews some of the key advances in the field. Part one covers materials, detector types, and devices, and includes discussion of silicon photonics, detectors based on reduced dimensional charge systems, carbon nanotubes, graphene, nanowires, low-temperature grown gallium arsenide, plasmonic, Si photomultiplier tubes, and organic photodetectors, while part two focuses on important applications of photodetectors, including microwave photonics, communications, high-speed single photon detection, THz detection, resonant cavity enhanced photodetection, photo-capacitors and imaging. We are always looking for ways to improve customer experience on Elsevier. We would like to ask you for a moment of your time to fill in a short questionnaire, at the end of your visit. If you decide to participate, a new browser tab will open so you can complete the survey after you have completed your visit to this website. Thanks in advance for your time.
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Silicon photonic devices and integrated circuits have undergone rapid and significant progresses during the last decade, transitioning from research topics in universities to product development in corporations. Silicon photonics is anticipated to be a disruptive optical technology for data communications, with applications such as intra-chip interconnects, short-reach communications in datacenters and supercomputers, and long-haul optical transmissions. Bell Labs, as the research organization of Alcatel-Lucent, a network system vendor, has an optimal position to identify the full potential of silicon photonics both in the applications and in its technical merits. Additionally it has demonstrated novel and improved high-performance optical devices, and implemented multi-function photonic integrated circuits to fulfill various communication applications. In this paper, we review our silicon photonic programs and main achievements during recent years.
This comprehensive guide surveys single-point devices and their image counterparts covering the range from UV to far IR. Basic operations, performance parameters, and special features are presented in the context of application circuits. Special attention is given to issues of sensitivity and noise limits.
Table of Contents
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