PIN Photodetector - Jacobs University Bremen · Jacobs University Bremen 5 Photoconductive...
Transcript of PIN Photodetector - Jacobs University Bremen · Jacobs University Bremen 5 Photoconductive...
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PIN Photodetector
Rahul Dewan
30th March 2007Course Presentation
(Photonics and Optical Communication)
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Outline
● Photodetectors– Photoconductive Detectors– Photodiodes– PIN Photodiodes Ref: [3]
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Photodetectors● Optoelectronic detectors are devices used to
detect optical radiaton – in most cases optical powers.
● Detectors convert a photon flux into electronic charges or a current, which is then amplified and processed with electronic circuits.
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Photodetectors● Example:
● Types:– Simple semiconductor detector– Junction photodiodes
● PN Photodetector● PIN Photodetector
– Thermal detectors
10 GHz PIN Photodetector
Ref: http://www.oemarket.com
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Photoconductive detectors● Detectors can be simply built from just using
a p or n doped semiconductor.● Semiconductor band gaps are in the energy
range of a photon. ● E = hc/λ :: For Si with E = 1.14 eV, λ = 1um
Ref: [1]
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Photoconductive detectors
Ref: [1]
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Photoconductive detectors
● Drawbacks:– Severe thermal noise– Bulky size– Relatively slow response time.
● Idea:– Use junction semiconductor photodiodes
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PN Photodiode
Ref: [2]
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PN Photodiode Operation
Ref: [2]
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PN Photodiode
● Drawbacks:– Relatively slow response time– Specially for Si (depletion area smaller than
compared to the diffusion length)
● Idea:– Carriers should be generated where the field is
large– Add an intrinsic region in between
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PIN Photodiode
Ref: [2]
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PIN Photodiode● Advantages:
● Longer absorption– Higher efficiency
● Response time– PIN order of nanoseconds– PN order of tens of nanoseconds or more
● Capacitance of the device is reduced– Wider frequency response.– Smaller RC => higher speed
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PIN Photodiode● Materials
– Silicon: good sensitivity roughly between 400 nm and 1000 nm (best around 800900 nm)
– germanium (Ge): good sensitivity roughly between 600 nm and 1800 nm (best around 14001500 nm)
– indium gallium arsenide (InGaAs): good sensitivity roughly between 800 nm and 1700 nm (best around 13001600 nm)
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Device Optimization● Performance Characteristics
– response speed– quantum efficiency at desired wavelength– size of the active area– noise sensitivity etc.
● For e.g.– Application based on detection of unfocused
source of light● tradeoff between large active area and device
response time.
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Conclusion● Semiconductor photodetectors were discussed.● PIN photodiode, which has a wider space
charge zone is the efficient of the 3 discussed.● But PIN exhibits low internal gain in detection of
the photodiode.● One solution : use Avalanche Photodiodes.● Photodiode technology still continues to
advance yielding sophisticated and cost effective products.
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References
● Introduction to Optical Engineering (F.T.S. Yu and X. Yang, Cambridge
University Press)● Optoelectronics (E. Rosencher and B. Vinter, Cambridge
University Press)● http://www.rpphotonics.com/
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Thank you!Questions ?