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Concepts Of Physics MCQ Edition [Volume 2]PhysicsSemiconductors and Semiconductor Devices

In a p - n junction, the diffusion current exceeds the drift current in magnitude

Options

  1. Aunder no circumstances
  2. Bwhen the junction is unbiased
  3. Cwhen the junction is reverse-biased
  4. Dwhen the junction is forward-biased

Correct answer

D. when the junction is forward-biased

Step-by-step solution

In an unbiased p - n junction, the diffusion current and drift current are equal in magnitude and opposite in direction, making the net current zero. When the junction is reverse-biased, the width of the depletion region and the potential barrier increase. This opposes the diffusion of majority carriers, making the diffusion current negligible. The drift current, due to minority carriers, dominates. When the junction is forward-biased, the applied voltage opposes the built-in potential, reducing the potential barri

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