Concept:Avalanche breakdown occurs in wider depletion regions under strong reverse bias when accelerated carriers acquire sufficient energy to ionize lattice atoms by collision.
Formula:$$M = \frac{1}{1 - \left(\frac{V_R}{V_{\text{BR}}}\right)^n} \to \infty \quad (\text{as } V_R \to V_{\text{BR}})$$
Solution:- The applied reverse voltage establishes a high internal electric field across the wide depletion layer.
- Thermally generated minority carriers are accelerated to high kinetic energies.
- These carriers collide with lattice atoms, breaking covalent bonds and freeing new electron-hole pairs (impact ionization).
- The newly generated carriers are also accelerated, creating a cumulative multiplication cascade (avalanche effect).
Why other options are incorrect:- Option A: Direct quantum tunneling is the mechanism of Zener breakdown in heavily doped, narrow junctions.
- Option B: Majority carrier diffusion is the mechanism of forward conduction, not reverse breakdown.
- Option C: Photon emission characterizes radiative recombination in forward-biased LEDs, not reverse breakdown.
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