Question

When a forward bias voltage is applied to a p-n junction diode, it:

• A. Increases the potential barrier
• B. Decreases the potential barrier
• C. Increases the width of the depletion layer
• D. Converts it into an insulator

Hint:

Forward bias decreases both the depletion layer width and barrier potential, allowing current to flow easily through the diode.

Answer 1

The Correct Option is B

Concept: A p-n junction diode is formed when p-type semiconductor and n-type semiconductor materials are joined together. At the junction, electrons and holes combine and create a region called the depletion layer. This depletion region creates an electric field and a potential barrier that normally prevents free flow of current. The behavior of this barrier changes depending upon whether forward bias or reverse bias is applied.

Step 1: Understanding forward bias connection in a diode.
A diode is said to be forward biased when: \[ Positive\ terminal\ of\ battery\rightarrow p\text{-}side \] \[ Negative\ terminal\ of\ battery\rightarrow n\text{-}side \] This external voltage pushes charge carriers toward the junction. Electrons from n-side and holes from p-side move closer together.

Step 2: Studying the effect on depletion layer and potential barrier.
The applied forward voltage opposes the internal electric field already present at the junction. As a result: \[ Barrier\ Potential\ decreases \] At the same time: \[ Depletion\ Layer\ Width\ decreases \] This allows majority charge carriers to cross the junction more easily.

Step 3: Determining the correct option by comparing all statements.
Checking all options: Option A: \[ Increases\ potential\ barrier \] Incorrect because forward bias reduces barrier. Option B: \[ Decreases\ potential\ barrier \] Correct because current flow becomes easier. Option C: \[ Increases\ depletion\ width \] Incorrect because depletion width decreases. Option D: \[ Converts\ into\ insulator \] Incorrect because forward bias makes conduction easier. Therefore the correct effect is: \[ \boxed{Decreases\ the\ potential\ barrier} \] Hence option (B) is correct.