P N Junction

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.