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Avalanche Breakdown and Zener Breakdown
Oct 06, 2018

1)Avalanche Breakdown
With the increase of the reverse voltage, the electric field in the space charge region increases, and the energy obtained by the carriers in the barrier region also increases. When the reverse voltage approaches the breakdown voltage UB, these carriers with higher energies collide with neutral atoms in the space charge region and ionize, resulting in new electron-hole pairs. These newly generated electrons and holes are then re-energized by an electric field, colliding with other neutral atoms and ionizing them, producing more electron-hole pairs. This chain reaction continues, causing a sharp increase in the number of carriers in the space charge region, like an avalanche, causing a sharp increase in the reverse current, resulting in breakdown. So this breakdown is called avalanche breakdown. It
Avalanche breakdown usually occurs in PN junction with low doping concentration and high applied voltage. This is because the PN junction with lower doping concentration has a wider space charge region and more chances of collision ionization.

2)Zener Breakdown
When the reverse voltage increases to a certain value, a strong electric field can be established in the barrier region, which can directly pull out the valence electrons bound in the covalent bond, resulting in a large number of electron-hole pairs in the barrier region, forming a large reverse current, resulting in breakdown. The phenomenon that atoms in the barrier region are directly excited by a strong electric field is called Zener breakdown. It
Zener breakdown usually occurs in PN junction with high doping concentration. This is because of the high doping concentration of PN junction, the space charge region of the charge density is very large, the width is narrow, as long as a small reverse voltage, can establish a strong electric field, Zener breakdown.

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