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.
The light-emitting diode (LED) is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation.
The diode is encapsulated with a transparent cover so that emitted light can come out.
WORKING :
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.
At junction boundary, excess minority carriers recombine with majority carriers near the junction.
On recombination, energy is released in the form of photons.
When forward current is small, the light intensity is small. When forward current increases light intensity increases and reach a maximum.
ADVANTAGES :
Low operational voltage and less power.
Long life and ruggedness.
Fast action and no warm-up time required.