P-N junction diode : If a p-type semiconductor is combined with N-type semiconductor a junction is formed with two electrodes this is called ” P-N junction diode”.

Symbol :

Formation of depletion region at the function :

 

  1. If P-N junction diode is formed , some of the holes in p-type and some of the electrons in N-type are diffuse towards each other and recombine.
  2. Due to this , narrow region is formed on either side of the junction is called ” depletion region “.
  3. This region creates an electric field  and causes a potential is called ” barrier potential “.
  4. This potential barrier steps further diffusion of electrons and holes . 

 Variation of depletion region :

Forward bias :
  1. In forward bias , positive terminal of battery is connected to P-type and negative terminal is connected to N-type .
  2. Due to this , the holes and electrons are repelled and moved towards the junction .
  3. As a result , the width of deletion region decreases and current flows through the diode and is measured by millimeter (mA).

 Reverse Bias :

  1. In forward bias, positive terminal of battery is connect to N-type and negative terminal is connected to P-type .
  2. Due to this , the holes and electrons are attracted and moves away from the junction.
  3. As a result , the width of depletion region increases and no current flows through the diode

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