Question

If the forward bias voltage in a diode is increased, the width of the depletion region

• A. increases
• B. decreases
• C. fluctuates
• D. does not change

Hint:

Forward bias opposes the built-in potential, so more carriers reach the junction.

Answer 1

The Correct Option is B

Step 1: Understand the concept:
A p-n junction has a depletion region near the junction. It has no free carriers and only fixed ions. The junction has a built-in potential barrier across it.

Step 2: What forward bias does:
In forward bias the p side is joined to the positive terminal and the n side to the negative terminal. The applied voltage opposes the built-in barrier. So the barrier height drops.

Step 3: Effect on the width:
Free holes and electrons are pushed towards the junction. They neutralise some of the fixed ions in the depletion region. So the depletion region becomes narrower. A larger forward voltage shrinks it further.

Step 4: Check the options:
Option (1) is true for reverse bias, not forward bias. Option (3) is not correct because the width changes smoothly with the voltage. Option (4) is wrong because the width does depend on the bias.

Final Answer:
The depletion region becomes narrower, so the answer is option (2), decreases.