Question

Explain avalanche breakdown in a diode and zener breakdown in a zener diode.

Answer 1

The avalanche breakdown is observed in the Zener Diodes having breakdown voltage more than 8 V. In the reverse biased condition, the conduction will take place only due to the minority carriers. As we increase the reverse voltage applied to the Zener diode, these minority carriers tend to accelerated. Therefore, the kinetic energy associated with them increases. While traveling, these accelerated minority carriers will collide with the stationary atoms and impart some of the kinetic energy to the valence electrons present in the covalent bonds.
On the other hand, Zener Breakdown is observed in the Zener diodes having breakdown voltage ess than 5V or between 5 to 8 volts. When a reverse voltage is applied to a Zener diode, it causes a very intense electric field to appear across a narrow depletion region. Such an intense electric field is strong enough to pull some of the valence electrons into the conduction band by breaking their covalent bonds .these electrons then become free electrons which are available for conduction. A large number of such free electrons will constitute a large reverse current through the Zener diode and breakdown is said to have occurred due to the Zener effect..