The reduction in electrical resistance across the p–n junction of a semiconductor diode under a reverse voltage that occurs as a result of the quantum tunnelling of valence electrons to the conduction band, allowing substantial current to flow in the reverse direction.
The Zener effect occurs at a well-defined voltage threshold. This is in contrast with the Avalanche effect, which takes place at a higher reverse voltage, with a less precipitous change in resistance.
1940s; earliest use found in Journal of the Acoustical Society of America. Originally after Italian effetto Zener.