Practice portal › Semiconductor Electronics › p-n Junction Formation
Asked in GSEB Board March 2022 · Depletion region and barrier potential
Given: a p-n junction with its p-side held at the higher potential, which is what forward bias means.
Idea: the barrier potential is produced by the uncovered donor and acceptor ions left in the depletion layer, so anything that shrinks that layer shrinks the barrier.
Forward bias drives holes in from the p-side and electrons in from the n-side towards the junction, where they cover some of those exposed ions.
The depletion layer therefore narrows and the potential step across it falls below its built-in value.
A lower step lets far more majority carriers cross, which is why the forward current climbs sharply once the applied voltage approaches the barrier height.
So keeping a p-n junction in forward bias decreases the barrier potential.
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