Current as a function of potential difference for a Zen diode
The avalanche effect is the phenomenon that a self-amplifying electrical current can occur in a semiconductor or insulator. This flow is caused by the fact that free electrons in a strong internal electric field (10 - 40 MV / m) are accelerated to release other electrons in collisions with the material, which in turn undergo the same fate. There is an avalanche of electrons.
As long as the material in which the avalanche effect occurs through the developed heat does not undergo changes, the process is reversible. This is useful in semiconductor components like law diode, avalanche diode and avalanche transistors.
In many common semiconductor devices, such as diodes and transistors, however, the avalanche effect sets an upper limit to the operating voltage. If this upper limit is exceeded, irreparable damage is caused by the then-occurring avalanche effect. The effect is further enhanced by the positive temperature coefficient of the phenomenon.
If the avalanche effect occurs in a solid insulator, it is usually destructive; In a gas it sometimes finds useful use in certain types of gas discharge tubes. Also see
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