CBSE Class 12-science Answered

Hi dear,

Zener breakdown is due to high electric field at the junction which pulls the bound electron out from its covalent bond. The reverse current is caused by the newly formed hole-electron pair for highly doped diodes.

Avalanche breakdown is due to thermal collisions. The applied potential puts a carrier in the barrier that collides with a crystal ion thereby imparting sufficient energy to disturb the covalent bond. Now, another eletron-hole pair is generated. This vigorous cumulative effect is called avalanche breakdown.

Hope this satisfies your question.

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