(a) Write the important considerations which are to be taken into account while fabricating a p-n junction diode to be used as a Light Emitting Diode (LED). What should be the order of band gap of an LED, if it is required to emit light in the visible range? Draw a circuit diagram and explain its action.

(b) Draw the V-I characteristics of an LED. State two advantages of LED lamps over conventional incandescent lamps.

 

 
 
 
 
 

Answers (1)
S safeer

(a) While fabricating a p-n junction important consideration are the following:-

(i) they should be heavily doped.

(ii) Encapsulated with transparent cover for visible light. 

 

The order of bandgap of an L.E.D, if it required to emit light in the visible range is 1.8eV to 3eV.

When the diode is forward biased, electrons are sent from n to p-side and holes are sent from p to n-side, at junction boundary the excess minority carrier recombine here with majority carriers releasing energy in the form of photons.

(b) The two advantages of LED over ordinary lamps ;

  • law operational voltage
  • fast switching capacity

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