In a p-n junction diode under forward bias, how do the width of the depletion layer and the height of the potential barrier change?
Answer and explanation
Correct answer: B. Both the depletion layer width and barrier height decrease
- Step 1: In forward bias, the positive terminal of an external voltage source is connected to the p-type region and the negative terminal to the n-type region.
- Step 2: The applied electric field opposes the built-in electric field of the depletion zone, reducing the effective barrier height from to .
- Step 3: Majority carriers (holes from p and electrons from n) are pushed toward the junction, causing the physical width of the depletion layer to decrease significantly.
Answer
Both the depletion layer width and barrier height decrease.
Why not the others: Both increasing is the characteristic behavior under reverse bias; Opposite variation violates the electrostatic potential Poisson equation; Remaining unchanged neglects external applied fields.
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