Explain how a diode’s depletion region changes in forward and reverse bias. What effect does this have on current flow?

Solution & explanation

At a p–n junction, diffusion leaves fixed ions forming a depletion region and barrier. Forward bias opposes the barrier and narrows the region, allowing greater carrier injection and current. Reverse bias increases barrier and width, leaving a small leakage until breakdown. The junction is not a perfect on/off switch at one universal voltage.