Zener phenomenon - definition
Zener phenomenon - definition
Zener phenomenon is a physical mechanism occurring in a semiconductor p-n back-polarised junction, involving a rapid increase in current as a result of tunneling of electrons through the potential barrier. This effect occurs at a specific threshold voltage value, called Zener voltage, and is the basis for the operation of Zener diodes - elements used to stabilise voltage in Instrumentation systems.
Under reverse voltage conditions below the conduction threshold, the p-n junction behaves as insulator, conducting a minimum leakage current. However, when a critical voltage is reached, a strong deformation of the energy band in the semiconductors, allowing the electrons to tunnel from the valence band of the p region into the conduction band of the n region. This transfer takes place without crossing the total energy barrier, because it occurs on the principle of quantum effect, which distinguishes it from avalanche breakdown, based on collisions of electrons with the crystal lattice.
The Zener phenomenon occurs mainly in thin junctions with a high degree of doping, which reduces the width of the barrier layer, and thus reduces the breakdown voltage. In practice, it is used in stabilisation Diodes, allowing the output voltage to remain almost constant regardless of changes in the input voltage or load. This phenomenon is prevalent at breakdown voltages up to about 5-6 V, above which avalanche breakdown becomes the main mechanism.
A characteristic feature of the Zener phenomenon is its strong temperature dependence - low voltage Zener diodes have a negative temperature coefficient, which means, that the breakdown voltage decreases with increasing temperature. Thanks to this property, it is possible to design reference and compensation circuits, combining components using different conduction mechanisms. The Zener phenomenon is crucial for many applications in precision electronics, surge protection and power regulation.
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