Zener effect

The Zener effect, named after its discoverer Clarence Melvin Zener (1905-1993), is the occurrence of a current ( zener current) in blocking direction on a highly doped semiconductor barrier layer by free charge carriers.

Is the basis for the Zener effect -induced mutual displacement of the bias energy bands in the p- doped and n-doped region. This shift goes so far as to unoccupied states in the conduction band have the same energy as occupied states in the valence band. By this approach, it is electrons with a certain probability may be made without energy consumption from the valence band to move into the conduction band (tunnel effect).

For the " Zener breakdown " required minimum voltage is referred to as the Zener voltage or Zener voltage. For silicon diodes, the Zener voltage is about 2 to 5.5 V.

Technically, this effect is used in so-called Zener diodes whose threshold voltage is below 5.5V. In outweighs the avalanche or avalanche breakdown. Diodes with breakdown voltages above 5.5 V are often wrong also called Zener diodes. As an overarching term for Zener diodes and avalanche diodes has established the term "Z- diodes ".

Functionally important criterion is that the Zener breakdown has a negative temperature coefficient, as opposed to avalanche breakdown with a positive temperature coefficient. Consequence of this behavior is that the Z- diodes with a breakdown voltage of 5.6 V having a very low temperature coefficient. The superposition and mutual compensation of both effects ( zener and avalanche effect ) can thus produce relatively temperature stable zener diodes with threshold voltages ranging from 5.5V.