Concept:When the applied forward voltage exceeds the built-in potential barrier (\( V_{\text{applied}} > V_B \)), the opposition to majority carrier diffusion is largely removed, and current is limited mainly by the small bulk resistance.
Formula:$$I_f = I_0 \left( e^{\frac{e V_f}{\eta k_B T}} - 1 \right)$$
Solution:- Below \( 0.7\text{ V} \), the built-in potential barrier prevents most majority carriers from crossing the junction.
- Once \( V_f \ge 0.7\text{ V} \), the potential barrier is eliminated.
- The dynamic resistance of the depletion layer becomes negligible, and forward current increases exponentially with small voltage increments.
Why other options are incorrect:- Option A: Silicon behaves as an extrinsic semiconductor with finite resistance, not a superconductor.
- Option C: Forward conduction is driven by majority carriers injected across the junction.
- Option D: Mass covalent bond rupture is characteristic of high-voltage reverse breakdown, not normal forward conduction.
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