Question

The width of the depletion layer of a p-n junction diode

• A. increases in forward bias
• B. decreases in reverse bias
• C. increases in reverse bias
• D. remains constant
• E. depends on the material only

Hint:

Think of the depletion layer like a gate. Forward bias pushes the gate open (thinner), while reverse bias pulls the gate shut tighter (thicker), making it harder for current to flow.

Answer 1

The Correct Option is C

Concept:
Physics - Semiconductor Electronics.
Step 1: Understand the Depletion Layer.
The depletion layer is a region near the p-n junction that is void of free charge carriers (electrons and holes). It consists of immobile ionized donor and acceptor atoms.
Step 2: Analyze Forward Bias.
When a p-n junction is forward biased (p-side to positive, n-side to negative), the external field opposes the built-in potential. Free carriers are pushed toward the junction, causing the depletion layer to narrow.
Step 3: Analyze Reverse Bias.
When reverse biased (p-side to negative, n-side to positive), the external field strengthens the built-in potential. Holes in the p-region and electrons in the n-region are pulled away from the junction.
Step 4: Conclusion.
As carriers move away from the junction, more immobile ions are uncovered, thereby increasing the width of the depletion layer.