Important differences between Avalanche Breakdown and Zener Breakdown

Avalanche Breakdown

Avalanche breakdown is a phenomenon that occurs in certain diodes and semiconductor devices when a reverse bias voltage is applied.

Avalanche breakdown refers to a sudden increase in current flow through a semiconductor device when the applied reverse bias voltage exceeds a certain threshold. It occurs due to the ionization of carriers in the device’s depletion region, leading to a rapid multiplication of charge carriers.

Operating Principle:

Avalanche breakdown occurs in devices such as avalanche diodes or Zener diodes, where the doping concentration is high enough to enable impact ionization. When the reverse bias voltage exceeds the breakdown voltage, the electric field becomes strong enough to accelerate charge carriers, causing a chain reaction of carrier multiplication.

Characteristics of Avalanche Breakdown:

• Breakdown Voltage: Avalanche breakdown occurs when the reverse bias voltage reaches a specific threshold known as the breakdown voltage. This voltage level is determined by the device’s design and doping concentration, and it is typically higher for avalanche diodes compared to Zener diodes.
• Current Amplification: During avalanche breakdown, the multiplication of charge carriers leads to a significant increase in current flow through the device. This current amplification effect is desirable in some applications, such as voltage regulation and protection circuits.

Significance of Avalanche Breakdown:

• Voltage Regulation: Avalanche breakdown is utilized in voltage regulation circuits, where devices such as avalanche diodes or Zener diodes are used to maintain a constant voltage across a load. The breakdown voltage acts as a reference voltage, ensuring that the voltage remains stable despite variations in the input or load conditions.
• Transient Voltage Suppression: Avalanche breakdown plays a crucial role in protecting electronic circuits from voltage spikes or transients. Devices like transient voltage suppressor diodes utilize avalanche breakdown to quickly divert excessive voltage away from sensitive components, preventing damage.

Zener Breakdown

“Exploring a Key Phenomenon in Semiconductor Devices”

Zener breakdown is a fundamental concept in semiconductor physics that describes a specific type of voltage breakdown mechanism.

Zener breakdown refers to the phenomenon that occurs in a p-n junction diode when the reverse bias voltage exceeds a specific threshold known as the Zener voltage. It is named after Clarence Zener, who first described the mechanism behind this type of breakdown.

Operating Principle:

Zener breakdown occurs due to the quantum tunneling effect in the depletion region of a p-n junction diode. When the reverse bias voltage reaches the Zener voltage, the electric field across the depletion region becomes strong enough to cause the tunneling of charge carriers, resulting in a significant increase in current flow.

Characteristics of Zener Breakdown:

• Zener Voltage: The Zener voltage is a critical parameter in Zener breakdown. It represents the voltage at which the breakdown occurs in the diode. The Zener voltage is determined by the doping concentration and design of the diode and can be controlled during the fabrication process.
• Voltage Regulation: One of the key characteristics of Zener breakdown is its ability to provide voltage regulation in electronic circuits. Zener diodes, specifically designed to exhibit Zener breakdown, are often used as voltage references or voltage regulators to maintain a stable voltage across a load.

Significance of Zener Breakdown:

• Voltage Regulation: Zener breakdown plays a vital role in voltage regulation circuits, where Zener diodes are employed to maintain a constant voltage level despite variations in the input or load conditions. These diodes act as voltage references, ensuring a stable output voltage.
• Overvoltage Protection: Zener diodes also serve as crucial components in protecting sensitive electronic devices from overvoltage events. When the input voltage exceeds the breakdown voltage, the Zener diode enters the breakdown region, diverting excessive current away from the sensitive components and preventing damage.

Zener Breakdown vs. Avalanche Breakdown:

• Mechanism: Zener breakdown and avalanche breakdown are two distinct mechanisms of achieving voltage breakdown in diodes. Zener breakdown relies on the quantum tunneling of charge carriers, while avalanche breakdown occurs due to carrier multiplication through impact ionization.
• Breakdown Voltage: Zener breakdown typically occurs at lower voltages compared to avalanche breakdown. The breakdown voltage of Zener diodes is well-defined and can be controlled during the manufacturing process, whereas avalanche breakdown depends on factors such as doping concentration and device design.
• Temperature Dependence: Zener breakdown exhibits a more pronounced temperature dependence compared to avalanche breakdown. The Zener voltage of a diode can change significantly with temperature variations, making it necessary to consider temperature compensation techniques in certain applications.

Important differences between Avalanche Breakdown and Zener Breakdown

Question:

In a diode, the breakdown voltage is 10 V. Determine the breakdown mechanism (Avalanche or Zener) if the voltage across the diode is 12 V.

Solution:

Avalanche Breakdown and Zener Breakdown are two mechanisms that can occur in diodes when the reverse voltage applied exceeds the breakdown voltage. The breakdown mechanism depends on the diode construction and its characteristics.

Given:

Breakdown Voltage (V_bd) = 10 V

Voltage across the diode (V_d) = 12 V

To determine the breakdown mechanism, we compare the applied voltage with the breakdown voltage.

If V_d < V_bd, the breakdown has not occurred.

If V_d ≥ V_bd, the breakdown has occurred.

In this case, the voltage across the diode (12 V) is greater than the breakdown voltage (10 V). Therefore, the breakdown mechanism is Avalanche Breakdown.

Note: Avalanche Breakdown occurs in diodes where the breakdown voltage is exceeded due to the high electric field causing the generation and acceleration of charge carriers, resulting in a sudden increase in current. Zener Breakdown, on the other hand, occurs in diodes specifically designed for the Zener effect, where the breakdown voltage is well-defined, and the breakdown occurs due to the quantum tunneling of charge carriers.

Advisory Note: Article shared based on knowledge available on internet and for the Knowledge purpose only. Please contact Professional/Advisor/Doctor for treatment/Consultation.