Concept:Zener breakdown is governed by quantum mechanical band-to-band tunneling. Because semiconductor band gaps narrow slightly with increasing temperature, the tunneling barrier height decreases, allowing breakdown to occur at a lower reverse voltage.
Formula:$$E_g(T) = E_g(0) - \frac{\alpha T^2}{T + \beta} \implies \text{Tunneling probability increases} \implies V_Z \text{ decreases}$$
Solution:- As temperature rises, the energy band gap \( E_g \) decreases.
- This reduces the energy barrier that valence electrons must tunnel through to reach the conduction band.
- Consequently, tunneling occurs at lower reverse electric fields, decreasing the Zener breakdown voltage \( V_Z \) (negative temperature coefficient).
Why other options are incorrect:- Option B: The depletion layer thickness is determined by doping and voltage, and does not expand to infinity.
- Option C: Carrier mobility decreases with temperature due to increased lattice scattering.
- Option D: Standard operating temperatures do not turn semiconductors into plasma.
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