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Question

When a forward bias is applied to a p-n junction, it___________.


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Solution

p-n junction:

  1. A p-n junction is an interface or a boundary between two semiconductor material types, namely the p-type and the n-type, inside a semiconductor.
  2. A schematic diagram of a p-n junction is shown below.

Barrier Potential:

  1. The electric field that is produced in the depletion region acts as a barrier.
  2. External energy must be exerted to allow the electrons to get through the barrier of the electric field.
  3. The potential difference required for the electrons to be passed across the electric field is called the potential barrier.
  4. The barrier potential of a P-N junction depends on the type of material, amount of doping and temperature of the semiconductor. For silicon it is about 0.7V, for germanium, it is about 0.3V.

Forward biasing:

  1. The positive terminal of the battery is linked to the p-side of the p-n junction, while the negative terminal is connected to the n-side.
  2. The potential barrier is opposed by the forward bias voltage.
  3. As a result, the potential barrier is decreased, and the depletion layer thins.
  4. The migration of majority carriers from one region to another causes conduction across the p-n junction. When the p-n junction is forward biased, the resistance decreases.
  5. When a forward bias is applied to a p-n junction, it lowers the value of the potential barrier.
  6. The potential barrier opposes the applied voltage in the event of a forward bias.
  7. When a p-n junction is forward biased, the negative voltage pushes the hole forward while the positive voltage pushes the electron backward, giving the electron the energy to traverse the junction and join with the hole.
  8. As a result, the depletion layer is reduced, which lowers the potential barrier across the junction.
  9. As a result, the potential barrier at the intersection is minimized.

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