Pn Junction Diode: Depletion Region

Depletion Region in Pn Junction

Formation of Depletion Region

• The depletion region is a region in a Pn junction where the concentration of charge carriers is depleted.
• It is formed when a p-type semiconductor and an n-type semiconductor are brought together.
• The p-type semiconductor has an excess of holes (positive charge carriers), while the n-type semiconductor has an excess of electrons (negative charge carriers).
• At the junction, the electrons from the n-type semiconductor flow into the p-type semiconductor, filling some of the holes.
• Similarly, the holes from the p-type semiconductor flow into the n-type semiconductor, filling some of the electrons.
• This process is known as diffusion.

Characteristics of Depletion Region

• The depletion region is a region of high resistance due to the lack of charge carriers.
• It is also known as the space charge region or the depletion layer.
• The width of the depletion region depends on the concentration of charge carriers in the p-type and n-type semiconductors.
• The depletion region acts as a barrier to the flow of charge carriers across the junction.

Depletion Region Width

• The width of the depletion region can be calculated using the following formula:

W = √(2ε(Vbi - V)/q * (Na + Nd) / (Na * Nd))

• Where:
  • W is the width of the depletion region
  • ε is the permittivity of the semiconductor material
  • Vbi is the built-in voltage
  • V is the applied voltage
  • q is the charge of an electron
  • Na is the concentration of acceptors in the p-type semiconductor
  • Nd is the concentration of donors in the n-type semiconductor

Importance of Depletion Region

• The depletion region plays a crucial role in the operation of Pn junction diodes.
• It allows the diode to control the flow of current across the junction.
• The depletion region can be manipulated by applying an external voltage to the diode, allowing it to be used as a rectifier, switch, or amplifier.

Learn about the depletion region in a Pn junction, its formation, characteristics, and importance in the operation of Pn junction diodes. Understand how to calculate the width of the depletion region and its role in controlling the flow of current.