Light-emitting diode

Definition: Light-emitting diode is a p-n junction, a semiconductor-based optoelectronic device, driven by a current I into forward bias. Electrons and holes recombine close to the junction between the p- and n-materials and give out radiation with a frequency determined by the photon energy which in turn is determined by the material’s impurities or band gap. Some fraction of the forward current I is then turned into useful light L (power) formed from photons with a mean energy hf_{m}. The quantum efficiency is eta = (eL/hf_{m}I). The more efficient light emitting diodes have a well-defined recombination region (volume Phi).

Alternative definition: An LED is a semiconductor device in which light is generated when an electric current is passed through it. The generated light has a wider spectral width and lower output power compared to a laser. However, LEDs have the advantage of being fairly inexpensive and portable.


References: J.E. Carroll. Rate Equations in Semiconductor Electronics. Cambridge University Press, 1990.

Related terms: emitter, source, laser, transmitter  

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