Question

The effect of reverse bias in a junction diode on its potential barrier is:

• A. increases
• B. decreases
• C. remains same
• D. None of these

Hint:

Reverse bias \(\Rightarrow\) barrier increases \(\Rightarrow\) current nearly zero.

Answer 1

The Correct Option is A

To understand the effect of reverse bias on the potential barrier of a junction diode, we need to delve into the basics of how a diode operates and what occurs during reverse biasing.

1. The junction diode is formed by joining n-type and p-type semiconductors. During its formation, electrons from n-type and holes from p-type diffuse into the opposite type, causing recombination near the junction and creating a depletion region.
2. This depletion region is void of free charge carriers and acts as an insulating layer. The fixed ions in the depletion region create a built-in electric field, establishing a potential barrier which opposes further diffusion of charge carriers.
3. Under reverse bias, the p-side is connected to the negative terminal of the battery, and the n-side to the positive terminal. This external voltage increases the built-in potential.
4. As the reverse bias voltage increases, it widens the depletion region, thereby increasing the potential barrier. This happens because the applied reverse voltage adds to the built-in potential of the junction, opposing further movement of majority carriers and enlarging the depletion zone.
5. Since the potential barrier height increases, the current flow through the diode is significantly reduced, typically to a negligible level unless breakdown conditions are reached.

With this explanation, we can conclude that the correct effect of reverse bias on a junction diode's potential barrier is that it increases the barrier.

Correct Answer: Increases

Let's rule out the other options:

• Decreases: Reverse bias does not decrease the potential barrier; it actually increases it by further depleting the region.
• Remains same: If the reverse bias did not change the potential barrier, there would be no effect on the depletion region width, contrary to observed behavior.
• None of these: Since 'Increases' is the correct response, this option is incorrect.