Concept:The forward bias applied electric field opposes the built-in electric field of the space-charge region, decreasing the net barrier height.
Formula:$$E_{\text{net}} = E_{\text{built-in}} - E_{\text{applied}}$$
Solution:- Majority carriers (holes in P-region, electrons in N-region) are pushed into the depletion layer.
- This reduces the width of the region containing uncompensated immobile ions.
- Consequently, the depletion width narrows, lowering junction resistance and permitting current flow.
Why other options are incorrect:- Option B: Widening of the depletion layer and an increased barrier potential occur during reverse biasing.
- Option C: Immobile donor and acceptor ions remain chemically fixed in the crystal lattice; their space-charge region narrows but is not neutralized at zero or sub-barrier voltages.
- Option D: Biasing changes the magnitude of the barrier potential, but it does not invert the physical polarity of the fixed ionic lattice charges.
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