Question

Break down voltage of a diode is \(5 \mathrm{~V}\). By which effect this breakdown occurs in diode? (A) Only avalanche effect (B) Only zener effect (C) Avalanche or zener effect (D) None of the above

Short answer

Based on the given breakdown voltage of 5V, the breakdown in this diode most likely occurs due to the zener effect. The correct answer is (B) Only zener effect.

Step-by-step solution

Understanding the Avalanche and Zener Effects.

The avalanche effect and zener effect are two primary mechanisms for the breakdown of diodes. Avalanche effect occurs when the electric field across the depletion region becomes so strong that it accelerates the free electrons to the point where, upon colliding with the semiconductor's atoms, they cause secondary ionizations, producing more free carriers. This results in a sudden rise in current, leading to an avalanche of free electrons. Avalanche effect usually occurs when breakdown voltage is above 6V. Zener effect, on the other hand, occurs typically in heavily doped semiconductors with breakdown voltage lower than 6V. A strong electric field across the depletion region can cause a significant number of valence electrons to "tunnel" from the valence band to the conduction band, creating a pronounced increase in current flow.

Evaluate given breakdown voltage

We are given that the breakdown voltage of the diode is 5V. Since the zener effect occurs when the breakdown voltage is lower than 6V, we can infer that the breakdown in this case might be due to the zener effect.

Identify the correct option

Based on the given information and our analysis, we can determine that the breakdown in this case is most likely due to the zener effect. Therefore, the correct option is: (B) Only zener effect

Key concepts

Avalanche Effect

The avalanche effect is a phenomenon that occurs in diodes when the electric field across the depletion region becomes extremely strong. This effect is most commonly observed in diodes with a breakdown voltage higher than 6 volts.
When the electric field is strong enough, it can accelerate free electrons to high speeds, causing them to collide with the atoms in the semiconductor material. These collisions lead to the creation of additional free charge carriers due to a process known as impact ionization. Each collision frees more electrons, resulting in a chain reaction or 'avalanche' which significantly increases the current through the diode.
Key features of the avalanche effect include:

• A sudden increase in current due to high-energy collisions.
• Primarily occurs at higher breakdown voltages.
• Dependent on the electric field strength and the semiconductor material properties.

Understanding this effect is crucial for designing and analyzing components that require precise voltage control, as it helps determine how diodes behave under high voltage stress.

Zener Effect

The zener effect is a critical concept in semiconductor physics, especially relevant in the functioning of Zener diodes. It is observed when the breakdown voltage is lower than 6 volts, typically in heavily doped diodes. This effect allows certain diodes to maintain a constant voltage output while conducting backward (reverse) current.
In the zener effect, the strong electric field across the depletion region enables electrons to tunnel through the energy barrier from the valence band to the conduction band. This quantum tunneling results in a sudden increase in reverse current, allowing the diode to stabilize the voltage.
Important aspects of the Zener effect include:

• Predominance in heavily doped semiconductors.
• Occurs at lower voltage levels, typically below 6 volts.
• Initiated by quantum tunneling, not by impact ionization (unlike avalanche).

The zener effect is particularly useful in voltage regulation circuits. It provides a simple and efficient way to ensure a stable voltage supply across various components in an electronic system.

Semiconductor Physics

Semiconductor physics forms the backbone of modern electronics, providing insight into how devices like diodes, transistors, and integrated circuits operate. Semiconductors are materials with electrical conductivity between that of conductors and insulators, making them ideal for controlling electrical currents.
These materials are primarily characterized by their band structure, which includes a valence band filled with electrons and a conduction band that is typically empty. The gap between these bands, known as the bandgap, determines the semiconductor's efficiency and type of conduction.
In diode operation, semiconductor physics explains several important phenomena:

• The creation of the depletion region at the p-n junction where electron-hole combinations occur, leading to an internal electric field.
• The mechanisms behind carrier flow under forward and reverse bias, essential for diode rectification and breakdown effects.
• Material properties, such as doping levels, which affect the threshold and breakdown voltages.

By understanding these concepts, one can appreciate how semiconductors enable the precise control of electrical characteristics in circuits, facilitating everything from simple diodes to complex computing devices.