Draw the V-I characteristic for LED and explain its working.
Answers
The “Light Emitting Diode” or LED as it is more commonly called, is basically just a specialised type of diode as they have very similar electrical characteristics to a PN junction diode. This means that an LED will pass current in its forward direction but block the flow of current in the reverse direction.
A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.
the V-I characteristic for LED is as follow:--
LED is light emitting diode which is heavily doped forward biased p-n junction which convert electric energy into optical energy.
The shorter lead responds to n or cathode side while longer lead corresponds to p or cathode side.The junction is made up of gallium arsenide.
When it is forward biased light photons are emitted from non metallised surface of n region to p region and holes from p to n region .Near junction concentration of minority carrier increases .
On either side the excess minority carriers combine with majority carriers.On recombination energy is released in form of photons.Photons with energy equal or lightly less than band gap are emitted.
As current increases in forward bias intensity of light increases and reaches maximum and further increase in current decreases the light intensity.
For visible spectrum energy gap of semiconductor is from 1.8 eV to 3 eV. The light corresponding to 1.8 eV is red and 3 eV light is violent.
For infrared gap is 1.4 eV.
