Photoconductivity

Source: Wikipedia, the free encyclopedia.

Photoconductivity is an

gamma radiation.[1]

When light is absorbed by a material such as a

impurities within the band gap. When a bias voltage and a load resistor are used in series with the semiconductor, a voltage drop
across the load resistors can be measured when the change in electrical conductivity of the material varies the current through the circuit.

Classic examples of photoconductive materials include:

Molecular photoconductors include organic,[6] inorganic,[7] and – more rarely – coordination compounds.[8][9]

Applications

Further information: Photoresistor

When a photoconductive material is connected as part of a circuit, it functions as a

phototransistors—but they are among the most common. Some photodetector applications in which photoresistors are often used include camera light meters, street lights, clock radios, infrared detectors, nanophotonic systems and low-dimensional photo-sensors devices.[10]

Sensitization

Sensitization is an important engineering procedure to amplify the response of photoconductive materials.[3] The photoconductive gain is proportional to the lifetime of photo-excited carriers (either electrons or holes). Sensitization involves intentional impurity doping that saturates native recombination centers with a short characteristic lifetime, and replacing these centers with new recombination centers having a longer lifetime. This procedure, when done correctly, results in an increase in the photoconductive gain of several orders of magnitude and is used in the production of commercial photoconductive devices. The text by Albert Rose is the work of reference for sensitization.[11]

Negative photoconductivity

Some materials exhibit deterioration in photoconductivity upon exposure to illumination.

hydrogenated amorphous silicon (a-Si:H) in which a metastable reduction in photoconductivity is observable[13] (see Staebler–Wronski effect). Other materials that were reported to exhibit negative photoconductivity include ZnO nanowires,[14] molybdenum disulfide,[15] graphene,[16] indium arsenide nanowires,[17] decorated carbon nanotubes,[18] and metal nanoparticles.[19]

Under an applied AC voltage and upon UV illumination,

metal-insulator transition at room temperature. The responsible mechanism for both transitions has been attributed to a competition between bulk conduction and surface conduction.[14] The frequency-driven bulk-to-surface transition of conductivity is expected to be a generic character of semiconductor nanostructures with the large surface-to-volume ratio
.

Magnetic photoconductivity

In 2016 it was demonstrated that in some photoconductive material a magnetic order can exist.[20] One prominent example is CH3NH3(Mn:Pb)I3. In this material a light induced magnetization melting was also demonstrated[20] thus could be used in magneto optical devices and data storage.

Photoconductivity spectroscopy

Main article: Photocurrent § Photocurrent spectroscopy

The characterization technique called photoconductivity spectroscopy (also known as photocurrent spectroscopy) is widely used in studying optoelectronic properties of semiconductors.[21][22]

See also

References

  1. PMID 634229
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  2. doi:10.1016/j.sna.2016.05.050
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  3. ^
    ISBN 978-0-07-162935-5
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  4. doi:10.1021/cr00017a020
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  5. ISSN 0022-3093
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  6. PMID 19848380
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  7. S2CID 234883317
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  8. ISSN 1387-7003
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  9. S2CID 215809603
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  10. doi:10.1088/1367-2630/aaad41
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  11. ISBN 0-88275-568-4
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  12. ISBN 978-0-8247-8321-1
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  13. ISSN 0003-6951
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  14. ^
    ISSN 0003-6951
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  15. ISSN 0031-8965
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  16. S2CID 118531249
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  17. PMID 29171260
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  18. ISSN 0921-5107
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  19. S2CID 4425298
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  20. ^
    PMID 27882917
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  21. ^ "RSC Definition - Photocurrent spectroscopy". RSC. Retrieved 2020-07-19.
  22. ^ Lamberti, Carlo; Agostini, Giovanni (2013). "15.3 - Photocurrent spectroscopy". Characterization of Semiconductor Heterostructures and Nanostructures (2 ed.). Italy: Elsevier. pp. 652–655.
    ISBN 978-0-444-59551-5
    .
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