A SIMPLE explanation of Avalanche Breakdown. Understand what Avalanche Breakdown (or “the Avalanche effect”) is, and how it is different from Zener Breakdown. You can read more about Avalanche Breakdown at: www.electrical4u.com/avalanch...
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Avalanche breakdown (or “the avalance effect”) is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good insulators. It is a type of electron avalanche. The avalanche process occurs when carriers in the transition region are accelerated by the electric field to energies sufficient to create mobile or free electron-hole pairs via collisions with bound electrons.
There is a difference between Avalanche breakdown and Zener breakdown. In Zener breakdown, the electrons “tunnel” from the valence band of the p side to the conduction band on the n side. In classical physics, electrons should not have been able to cross over in this way. Tunnelling is, in fact, a quantum mechanical phenomenon, which comes about from electrons having wave properties.
The main differences between Zener and Avalanche Breakdown are:
1. Zener breakdown and avalanche breakdown are processes by which diodes begin to conduct significant currents, when they are subject to a high reverse voltage.
2. Zener breakdown occurs when the doping levels are high, and involves electrons tunnelling from the valence band of the p side to the conduction band on the n side.
3. Avalanche breakdown occurs when charge carriers which are accelerated by the electric field gain enough kinetic energy such that, when they collide with lattice atoms, they ionise the lattice atoms to produce electron-ion pairs. These pairs, in turn, cause further ionisations, leading to an “avalanche” effect.
1 сен 2016
