Zener effect

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IU characteristics of Zener diodes. Zener and Avalanche breakthroughs in the lower left quadrant.

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

The basis for the Zener effect is a mutual displacement of the energy bands in the p-doped and in the n-doped area caused by bias . This shift goes so far that unoccupied states in the conduction band have the same energy as occupied states in the valence band . This approximation makes it possible for electrons to move from the valence band into the conduction band with a certain probability without absorbing energy ( tunnel effect ).

The minimum voltage required for the "Zener breakdown" is known as the Zener voltage or the Zener voltage . With silicon diodes , the Zener voltage is between 2 V and 5.5 V.

This effect is used technically with so-called Zener diodes . At a threshold voltage below 5.5 V, the Zener effect predominates, at voltages above the avalanche or avalanche breakdown predominates . Diodes with breakdown voltages above 5.5 V are colloquially incorrectly referred to as Zener diodes. The term "Zener diodes" has established itself as a general term.

The Zener breakdown occurs in highly doped pn junctions . Due to the high doping, the space charge zone formed is very thin, a prerequisite for the tunnel effect. The negative temperature coefficient for a specific Zener diode based on the Zener breakdown is in the range of −3 mV / K, is largely independent of the level of the specific breakdown voltage of the Zener diode and reduces the breakdown voltage with increasing temperature.

literature

  • Dieter Zastrow: Electronics . 2nd Edition. Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden 1984, ISBN 3-528-14210-3 .
  • Joachim Specovius: Basic course in power electronics - components, circuits and systems. 9th edition, Springer Verlag, Wiesbaden 2018, ISBN 978-3-658-21168-4 .

Web links

Individual evidence

  1. ↑ Joachim Specovius: Basic course in power electronics - components, circuits and systems . 9th edition. Springer Fachmedien Wiesbaden GmbH, Beuth University of Applied Sciences Berlin Berlin, Germany 2018, ISBN 978-3-658-21168-4 , p. 16 .
  2. ^ Zener and Avalanche Breakdown / Diodes, Engineering Sciences 154. Retrieved December 29, 2014 .