As an expert in the field of electronics, I've spent considerable time studying the behavior of various diodes, including the Zener diode. The Zener diode is a unique type of diode that is specifically designed to operate in a reverse-biased condition, and it has a very important role in electronic circuits.

The Zener diode is characterized by its ability to maintain a constant voltage across its terminals when it is in the reverse breakdown region. This is achieved through a special doping process that creates a very sharp junction between the P-type and N-type semiconductor materials. The high doping levels result in a narrow depletion region, which is crucial for the Zener effect to occur.

In a normal diode, when it is reverse-biased, the current flow is minimal up to the breakdown voltage of the diode. However, the Zener diode is designed to allow a significant current to flow once the reverse voltage reaches a certain level, known as the Zener voltage. This is not a failure mode but a controlled process that is utilized in circuits for various applications.

The operation of a Zener diode in reverse bias can be better understood by looking at the energy band diagram. Under reverse bias, the depletion region widens, increasing the electric field across the junction. When the electric field reaches a critical level, it is strong enough to ionize the covalent bonds in the semiconductor material, creating electron-hole pairs. This process is known as impact ionization and results in a rapid increase in current, which is the hallmark of the Zener breakdown.

The Zener breakdown occurs at a precise voltage, which is determined by the doping levels and the material properties of the diode. This makes the Zener diode an ideal component for voltage regulation and reference applications. It can be used to create a stable reference voltage in circuits, ensuring that other components receive a consistent voltage level regardless of variations in the power supply or load conditions.

Moreover, the Zener diode is also used in clamping circuits to protect sensitive components from voltage spikes. When a voltage spike occurs, the Zener diode quickly enters the breakdown region, clamping the voltage to a safe level and preventing damage to the circuit.

In summary, the Zener diode is used in reverse bias because of its unique ability to maintain a stable voltage across its terminals once it enters the reverse breakdown region. This characteristic makes it invaluable for voltage regulation, reference voltage applications, and protection circuits.

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Zener diodes are highly doped diodes. This means their behavior in forward bias will be same as a normal diode. But while in reverse bias their junction potential is increased. ... So that means when the voltage crosses 6V then the diode is in Reverse breakdown and hence the current through the diode increases rapidly.read more >>