Question

The reverse biasing in a junction diode,

• A. increases the number of majority charge carriers
• B. increases the number of minority charge carriers
• C. reduces the number of minority charge carriers
• D. decreases the potential barrier
• E. increases the potential barrier

Hint:

Forward bias ↓ barrier, Reverse bias ↑ barrier.

Answer 1

Answer: (E)

Step 1: Understanding Reverse Biasing:
A p-n junction diode is reverse biased when the positive terminal of an external voltage source is connected to the n-type material and the negative terminal is connected to the p-type material.
Step 2: Effect on Charge Carriers and Depletion Region:
In this configuration, the applied external electric field is in the same direction as the internal electric field of the potential barrier. This has two main effects:
The external voltage pulls the majority charge carriers (holes in the p-side and electrons in the n-side) away from the junction.
As the majority carriers move away, more immobile charged ions are left uncovered near the junction.
This process leads to a widening of the depletion region.
Step 3: Effect on the Potential Barrier:
The potential barrier is the potential difference that exists across the depletion region. Since reverse biasing widens the depletion region, it strengthens the internal electric field and increases the potential difference across it. Therefore, reverse biasing increases the potential barrier. This increased barrier makes it even more difficult for majority carriers to cross the junction, effectively blocking the current (except for a very small leakage current due to minority carriers).
Step 4: Evaluating the Options:
(A), (B), (C): Biasing does not change the intrinsic number of charge carriers. Incorrect.
(D) decreases the potential barrier: This happens in forward biasing. Incorrect.
(E) increases the potential barrier: This is the primary effect of reverse biasing. Correct.