How does Zener phenomenon differ from Avalanche breakdown?

When subjected to conditions of reverse bias, the behaviour of a p-n junction diode may be described using one of two distinct mechanisms:

  • The Zener Breakdown and
  • The Avalanche Breakdown.

Both mechanisms lead to the breakdown of the p-n junction; however, their observable processes and distinguishing features are distinct from one another.

What is Zener Breakdown?

The phenomenon known as Zener breakdown occurs when a strong electric field is given to a p-n junction.

This causes the valence-electrons in the depletion area to tunnel through the junction and enter the conduction band, which results in a large number of electron-hole pairs being produced.

This leads to an abrupt rise in the amount of reverse current that is flows through the diode, which has the potential to bring about the diode’s failure.

Zener breakdown normally takes place in highly doped p-n junctions, & the doping concentration is that determines the voltage at which it occurs.

What is Avalanche Breakdown?

Avalanche breakdown, on the other side, happens when the electric field in the depletion (depletion layer) region is strong enough to make the acceleration (momentum) of the free electrons in the junction.

This acceleration causes the free electrons to collide with atoms in the crystal lattice, which then knocks additional electrons loose from their bonds.


This sets off a chain reaction, which leads to a significant rise in the reverse current as well as a significant increase in the number of electron-hole pairs.

The breakdown voltage is dictated by the thickness of the depletion area, which is typical of where avalanche breakdown occurs, which is in weakly doped p-n junctions.

Zener Breakdown vs Avalanche Breakdown

Zener breakdown takes place in heavily doped p-n junctions, & the breakdown voltage is determined by the doping concentration.

Avalanche breakdown, on the other side, takes place in lightly (small) doped p-n junctions & the breakdown voltage is obtained by the thickness of the depletion region.

In both conditions, the doping concentration has an influence on determining the breakdown voltage.