# How is a light emitting diode fabricated? Briefly explain the basic processes involved in the emission of spontaneous radiation from it. Write two advantages of LED lamps over the incandescent low power lamps.

$\Rightarrow$ The light-emitting diode (LED) is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation.

$\Rightarrow$ The diode is encapsulated with a transparent cover so that emitted light can come out.

WORKING :

$\Rightarrow$ When the diode is forward biased, electrons are sent from n region to p region and holes are sent from p region to n region.

$\Rightarrow$ At junction boundary, excess minority carriers recombine with majority carriers near the junction.

$\Rightarrow$ On recombination, energy is released in the form of photons.

$\Rightarrow$ When forward current is small, the light intensity is small. When forward current increases light intensity increases and reach a maximum.

$\Rightarrow$ Low operational voltage and less power.

$\Rightarrow$ Long life and ruggedness.

$\Rightarrow$ Fast action and no warm-up time required.

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