Step 1: Understand the p-n junction under forward bias.
A p-n junction diode has a potential barrier at the junction due to charge separation, forming a depletion layer devoid of mobile charge carriers. This potential barrier is approximately 0.7 V for silicon diodes at equilibrium.
Step 2: Analyze the effect of forward bias.
Forward biasing a p-n junction connects the positive terminal to the p-side and the negative terminal to the n-side. This diminishes the electric field that opposes majority carrier diffusion:- The applied voltage counteracts the built-in potential barrier, thus lowering its height.
- A lower potential barrier weakens the electric field across the depletion region, facilitating easier diffusion of majority carriers (electrons from the n-side and holes from the p-side) across the junction.
Step 3: Determine the effect on the depletion layer width.
The depletion layer width is contingent on the electric field and potential barrier. During forward bias:- The reduced potential barrier leads to a weakened electric field across the junction.
- Consequently, the depletion layer narrows as the space charge region contracts due to enhanced carrier diffusion.
Step 4: Summarize the effects.
- The potential barrier height decreases as the forward bias opposes the built-in potential.
- The depletion layer width decreases because the weakened electric field allows the depletion region to contract.
Step 5: Match with the options.
Both the potential barrier height and the depletion layer width decrease, corresponding to option (A).