A diode is basically a PN junction device. P type semiconductors are rich in holes while N types are rich in electrons. (Rich means majority carriers here, which are found in the outer shell of atoms).
Thus at the junction of this P and N type material, electrons and holes will combine resulting in a deficiency of charge carriers. This is termed the depletion region.
When you attach the negative terminal of a battery to the N end of the diode and the positive terminal to the P end, the electrons will be repelled towards the junction and holes too will move towards the junction region, making it thin (narrow) (Further increase in voltage will make current to pass through). The opposite occurs when they are connected the other way. The region becomes thin.
For normal operations, zener diodes are connected in reverse (diodes usually are connected reversely unless you want drop some voltage) the depletion layer widens, as described above. But at a certain reverse voltage, the zener starts to conduct suddenly. This is called avalanche/breakdown voltage. How the layer becomes thin (if at all, seems improbable) when they are reverse connected, I do not know.
The maximum reverse bias potential that can be applied to a Zener diode before it enters the Zener region is called the "Zener breakdown voltage" or "Zener voltage." This is the point at which the diode begins to conduct in reverse bias due to the Zener effect, allowing it to stabilize voltage across a load. Exceeding this voltage can lead to thermal runaway or damage if not properly managed.
zener cut in voltage
Reverse Bias
If PN regions in a Zener diode are heavily doped, the breakdown voltage decreases due to the increased electric field strength at the junction. This heavy doping leads to a thinner depletion region, allowing the Zener breakdown to occur at lower voltages. Consequently, such a Zener diode can effectively regulate voltage at a specified lower level, making it suitable for low-voltage applications. However, excessive doping may also affect the diode's stability and performance characteristics.
This space is for answering "http://wiki.answers.com/Q/Why_does_voltage_remain_constant_in_the_reverse_breakdown_region_in_a_zener_diode" Why does voltage remain constant in the reverse breakdown region in a zener diode?
Zener diodes are heavily doped to create a narrow depletion region, allowing them to operate in the reverse breakdown region where they exhibit the Zener effect. This effect causes the diode to conduct in reverse bias at a specific voltage, ideal for voltage regulation applications.
The zener diode protects the meter by stabilizing the voltage when it goes in to the breakdown region.
zener resistance of a zener diode is the resistance of the zener diode but which is the resistance of a diode
In a Zener diode, tunneling effect occurs when charge carriers are able to pass through the thin depletion region by quantum mechanical tunneling. This allows the diode to start conducting at lower voltages than normally expected. The tunneling effect in Zener diodes is responsible for their ability to regulate voltage by maintaining a constant breakdown voltage.
The maximum reverse bias potential that can be applied to a Zener diode before it enters the Zener region is called the "Zener breakdown voltage" or "Zener voltage." This is the point at which the diode begins to conduct in reverse bias due to the Zener effect, allowing it to stabilize voltage across a load. Exceeding this voltage can lead to thermal runaway or damage if not properly managed.
If the zener diode is in zener breakdown the voltage across the zener diode remains constant regardless of current (for the ideal zener diode). Real zener diodes have parasitic resistance that causes the voltage across the zener diode to increase slightly with increased current, but due to temperature dependant variations in this parasitic resistance as well as temperature dependant variations in the zener breakdown voltage, this change in voltage in real zener diodes cannot be described by a simple linear factor.
An ordinary diode is designed to have a high breakdown voltage, causing it to experience avalanche breakdown when the reverse bias voltage surpasses its breakdown voltage. In contrast, a Zener diode is engineered with a specific doping profile that allows it to exhibit Zener breakdown at lower voltages by enabling electron tunneling across the depletion region. This fundamental difference in design leads to the distinct breakdown behaviors in each type of diode.
The zener region describes the area on the performance curve (a graph of voltage across versus current through the junction) of a zener diode. The diode acts like a "regular" diode in the forward biased direction. When some 0.7 volts or so is reached, forward current begins to climb rapidly as voltage is increased (for silicon diodes.) But in the reverse direction recall that as the diode is reverse biased, a small amount of current will flow (because of minority carriers). This "trickle" of current will continue until the "zener voltage" is reached, and then the diode will begin to conduct heavily. On the graph, this is the zener region. Zener diodes can be made to breakdown at a specific voltage, and their ability to conduct reverse current can be increased by manufacturing a larger diode. That means there are a range of voltages and wattages of zener diodes available. Wikipedia has more information and that graph. Use the link provided to get there.
The function of a zener diode is for it to act as a voltage regulator in the breakdown region.
zener cut in voltage
Reverse Bias
The difference between the pn-junction diode and the zener diode is that the pn-junction diode is used for rectification while the zener diode is used for rectification and stabilization. Also, the zener diode can function in the breakdown region while the pn-juntion diode can not function in that regime.