Carrier flow under reverse bias: does reverse-biasing a pn junction primarily allow majority carrier current to flow across the junction, or is reverse current mainly due to minority carriers?

Introduction / Context:
Understanding which carriers dominate under reverse bias is essential for diode leakage analysis, temperature effects, and breakdown phenomena. The statement claims reverse bias “allows the flow of majority current,” which conflicts with device physics.

Given Data / Assumptions:

• Standard pn junction below breakdown.
• Uniform temperature; no illumination (to avoid photogeneration).
• Small reverse current regime (leakage region).

Concept / Approach:
Under reverse bias, the depletion region widens and majority carriers are repelled from the junction, greatly suppressing majority conduction. The observed reverse current is dominated by minority carriers that are thermally generated and swept across the junction by the electric field. Only when breakdown (avalanche or Zener) occurs does a large current flow, but even then the current mechanism is not majority-carrier diffusion across a forward-like barrier.

Step-by-Step Solution:

Verification / Alternative check:
Leakage current’s strong temperature dependence supports minority carrier generation as the mechanism (higher temperature increases generation rate).

Why Other Options Are Wrong:
Correct: contradicts the physics of reverse-biased operation.

Only for Ge or only above breakdown: the statement is generally false below breakdown for both Si and Ge; breakdown introduces different mechanisms.

Common Pitfalls:
Confusing forward and reverse carrier roles; assuming any applied voltage “drives” majority carriers across regardless of bias polarity.

Final Answer:
Incorrect