Concept:Avalanche breakdown occurs in lightly doped junctions with wider depletion regions under high reverse voltages (typically \( > 6\text{ V} \)), where accelerated minority carriers gain enough kinetic energy to free bound electrons via impact ionization.
Formula:$$\text{Carrier Multiplication: } M = \frac{1}{1 - \left(\frac{V_R}{V_{BR}}\right)^n}$$
Solution:- Thermally generated minority carriers are accelerated by the reverse electric field across the wide depletion layer.
- These high-energy carriers collide with lattice atoms, breaking covalent bonds and freeing secondary electron-hole pairs.
- These newly freed carriers are accelerated in turn, triggering a chain reaction (avalanche multiplication) that produces a large reverse current.
Why other options are incorrect:- Option B: Direct field emission characterizes Zener breakdown in heavily doped junctions.
- Option C: Radiative recombination occurs in forward-biased LEDs, not reverse-biased avalanche breakdown.
- Option D: Avalanche breakdown is an electronic impact process, not a chemical dissociation of the crystal lattice.
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