Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 129 of 494
When a PN junction is reverse biased, what happens to the majority charge carriers in the P-type and N-type regions?
A
They cross the junction in large numbers to produce forward current
B
They are pulled away from the junction, widening the depletion region
C
They neutralize fixed donor and acceptor ions completely
D
They convert into photons that are emitted through the crystal surface
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: They are pulled away from the junction, widening the depletion region
Concept:

In reverse bias, the positive battery terminal connects to the N-side and the negative terminal to the P-side, exerting attractive electrostatic forces that pull majority carriers away from the junction.

Formula:

$$W_{\text{depletion}} \propto \sqrt{V_0 + V_R}$$

Solution:

  • Electrons in the N-region are drawn toward the positive battery terminal.


  • Holes in the P-region are drawn toward the negative battery terminal.


  • This widens the depletion layer and prevents majority carrier conduction across the junction.


Why other options are incorrect:

  • Option A: Majority carriers cross the junction during forward bias, not reverse bias.
  • Option C: Pulling carriers away exposes more fixed ions, increasing the depletion layer charge.
  • Option D: Radiative recombination occurs under forward bias in direct bandgap LEDs, not in reverse-biased diodes.

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