Depletion region of a PN junction is formed

Electrical Engineering XYZ MCQs

Depletion region of a PN junction is formed:

  1. During Forward bias
  2. During Heating
  3. During Manufacturing
  4. During Reverse bias

Correct answer: 3. During manufacturing

Related reading: Semiconductor Manufacturing Techniques

Explanation: The depletion region of a PN junction is formed during manufacturing. When a PN junction is created, it involves bringing together a P-type semiconductor (which has an excess of positive “holes” carriers) and an N-type semiconductor (which has an excess of negative electrons carriers). When these two materials are joined together, a region near the junction becomes depleted of mobile charge carriers.

This depletion region is formed due to the diffusion of charge carriers from the P-side to the N-side and from the N-side to the P-side. As a result, positive ions from the N-side migrate towards the P-side and negative ions from the P-side migrate towards the N-side. This movement of ions creates a region near the junction that is depleted of mobile charge carriers, hence it’s termed as the depletion region.

Once formed during manufacturing, the depletion region remains in place regardless of biasing conditions (forward or reverse bias). However, under reverse bias, the width of the depletion region increases, while under forward bias, it decreases. But its formation primarily occurs during the manufacturing process when the P-type and N-type semiconductors are brought together to create the PN junction.

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