Question

The following are the graphs of potential barrier versus width of the depletion region for a p-n junction diode.

Which of the following is correct?

• A. II
• B. III
• C. IV
• D. I

Hint:

When studying p-n junctions, remember that the depletion region width is widest for an unbiased diode and decreases when forward biased. For reverse bias, the depletion region width increases.

Answer 1

The Correct Option is D

The potential barrier in a p-n junction diode changes with the width of the depletion region depending on whether the diode is forward biased, reverse biased, or unbiased.
- When the diode is unbiased (open circuit), the depletion region is at its maximum width, and the potential barrier is the highest. 
- When the diode is forward biased, the depletion region narrows, and the potential barrier decreases. 
- When the diode is reverse biased, the depletion region widens and the potential barrier increases even more. In the graph: - Graph I represents the unbiased diode. - Graph II represents the forward biased diode. - Graph III represents the reverse biased diode. 
- Graph IV represents an unused diode, which doesn't influence the graph. 
Thus, the correct option is D.