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12 - Visible-spectrum LEDs

Published online by Cambridge University Press:  05 September 2012

E. Fred Schubert
Affiliation:
Rensselaer Polytechnic Institute, New York
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Summary

Originally, LEDs were exclusively used for low-brightness applications such as indicator lamps. In these applications, the efficiency and the overall optical power of the LED are not of primary importance. However, in more recent applications, for example traffic light applications, the light emitted by LEDs must be seen even in bright sunlight and from a considerable distance. LEDs with high efficiency and brightness are required for such applications.

In this chapter, low-brightness as well as high-brightness LEDs are discussed. GaAsP and nitrogen-doped GaAsP LEDs are suitable only for low-brightness applications. AlGaAs LEDs are suitable for low- as well as high-brightness applications. AlGaInP and GaInN LEDs are used in high-brightness applications.

The GaAsP, GaP, GaAsP:N, and GaP:N material systems

The GaAs1−xPx and GaAs1−xPx:N material system is used for emission in the red, orange, yellow, and green wavelength range. The GaAsP system is lattice mismatched to GaAs substrates, resulting in a relatively low internal quantum efficiency. As a result these LEDs are suitable for low-brightness applications only.

GaAs1−xPx was one of the first material systems used for visible-spectrum LEDs (Holonyak and Bevacqua 1962; Holonyak et al. 1963, 1966; Pilkuhn and Rupprecht 1965; Wolfe et al., 1965; Nuese et al. 1966). In the early 1960s, GaAs substrates were already available. Bulk growth of GaAs substrates was initiated in the 1950s and epitaxial growth by LPE and VPE started in the 1960s.

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Information
Light-Emitting Diodes , pp. 201 - 221
Publisher: Cambridge University Press
Print publication year: 2006

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  • Visible-spectrum LEDs
  • E. Fred Schubert, Rensselaer Polytechnic Institute, New York
  • Book: Light-Emitting Diodes
  • Online publication: 05 September 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511790546.013
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  • Visible-spectrum LEDs
  • E. Fred Schubert, Rensselaer Polytechnic Institute, New York
  • Book: Light-Emitting Diodes
  • Online publication: 05 September 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511790546.013
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Visible-spectrum LEDs
  • E. Fred Schubert, Rensselaer Polytechnic Institute, New York
  • Book: Light-Emitting Diodes
  • Online publication: 05 September 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511790546.013
Available formats
×