P-N-Junction

P – N Junction – Definition, Breaking down, and Applications

Introduction

The n-type semiconductor is developed by adding pentavalent impurities to the inherent semiconductor while the p-type semiconductor is formed by adding trivalent impurities to the inherent semiconductor.

Additionally, in n-type semiconductors, electrons are the majority carriers while holes are the minority carriers. On the other hand, in p-type semiconductors holes are the majority carriers while electrons are the minority carriers.

P-n joints are developed by joining up with n-type and also p-type semiconductor products. Because the n-type area has a high electron concentration as well as the p-type a high hole concentration, electrons diffuse from the n-type side to the p-type side.

Similarly, holes flow by diffusion from the p-type side to the n-type side.

n-p-type

Definition:

If the crystal of germanium or silicon is grown in such a way that it’s one half is doped with a trivalent impurity and the other half is doped with a pentavalent impurity, a p-n junction is formed.

P-N junction is also called a semiconductor diode. It is symbolically represented as the arrowhead represents the p region and the vertical line represents the n region.

Definition-p-n

The credit of exploration of the p-n junction goes to American physicist Russel Ohi of Bell Laboratories.

Depletion region

The electrons diffuse in p-type material just after the formation of the p-n junction. So, a charge-less region is formed around the junction, which contains no charge carriers i.e., mobile charges. This region is called the depletion region.

Biasing of P – n junction

If the battery of some emf is connected across a P-N junction, the junction is said to be a biased junction. This biasing can be done in two ways:

  • Forwarded Biased P-N junction

When an external potential is applied across the p-n junction in such a way that the positive terminal of the battery is connected with p-type and its negative terminal is connected with n-type, then it is called forwarded biased junction.

  • Reverse Biases P-N junction

When an external potential is applied across the p-n junction in such a way that the positive terminal of the battery is connected with the n-type and the negative terminal is connected with p-type, then it is called a reverse-biased p-n junction.

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Breaking down of P-N junction

When the reverse voltage is increased, the K.E of minority change carriers also increases till it is sufficient to break a covalent bond. As the covalent bond breaks, more electron-hole pairs are produced. So, the minority carriers begin to increase rapidly.

This increases the reverse current. The value of the reverse voltage at which the junction breaks down is called break down voltage. After the break down the reverse current increases sharply which damages the diode.

Applications

The P-n junction is likewise a basic foundation of numerous various other semiconductor digital gadgets such as transistors, solar batteries, light-emitting diodes, as well as integrated circuits.

Semiconductor devices are the basic building blocks of all electronic gadgets such as computers, control systems, ATM MACHINE (Automated Teller Machine), cellphones, amplifiers, and so on.

Diodes are the most basic type of all semiconductor devices. The different applications of diodes include computer systems, power products, television, radios, and so on.

MCQs about P – N Junction

  • What is a P-N junction?
    • A) A type of transistor
    • B) A type of solar cell
    • C) A semiconductor diode
    • D) A type of integrated circuit
    • Answer: C) A semiconductor diode
  • Who is credited with the exploration of the P-N junction?
    • A) Thomas Edison
    • B) Alexander Graham Bell
    • C) Nikola Tesla
    • D) Russel Ohi
    • Answer: D) Russel Ohi
  • What is the majority carrier in an n-type semiconductor?
    • A) Electrons
    • B) Holes
    • C) Protons
    • D) Neutrons
    • Answer: A) Electrons
  • What happens to form the depletion region in a P-N junction?
    • A) Electrons and holes combine
    • B) Electrons diffuse into the p-type material
    • C) Mobile charges accumulate around the junction
    • D) Holes flow into the n-type material
    • Answer: C) Mobile charges accumulate around the junction
  • How is a P-N junction biased in forward bias?
    • A) Positive terminal to p-type, negative terminal to n-type
    • B) Negative terminal to p-type, positive terminal to n-type
    • C) Positive terminal to both p-type and n-type
    • D) Negative terminal to both p-type and n-type
    • Answer: A) Positive terminal to p-type, negative terminal to n-type
  • What is the reverse biased P-N junction?
    • A) Positive terminal to both p-type and n-type
    • B) Negative terminal to both p-type and n-type
    • C) Positive terminal to p-type, negative terminal to n-type
    • D) Negative terminal to p-type, positive terminal to n-type
    • Answer: D) Negative terminal to p-type, positive terminal to n-type
  • What happens during the breakdown of a P-N junction?
    • A) Decrease in reverse current
    • B) Increase in minority carriers
    • C) Covalent bonds strengthen
    • D) Production of fewer electron-hole pairs
    • Answer: B) Increase in minority carriers
  • What is the break down voltage of a P-N junction?
    • A) The voltage applied in forward bias
    • B) The voltage at which covalent bonds form
    • C) The voltage causing a decrease in minority carriers
    • D) The voltage causing the junction to break down
    • Answer: D) The voltage causing the junction to break down
  • Which of the following is NOT an application of P-N junctions?
    • A) Transistors
    • B) Solar cells
    • C) Vacuum tubes
    • D) Light-emitting diodes
    • Answer: C) Vacuum tubes
  • What is the majority carrier in a p-type semiconductor?
    • A) Electrons
    • B) Holes
    • C) Protons
    • D) Neutrons
    • Answer: B) Holes
  • What is the depletion region?
    • A) A region where electrons and holes combine
    • B) A region with no charge carriers
    • C) A region of increased mobile charges
    • D) A region of decreased minority carriers
    • Answer: B) A region with no charge carriers
  • What happens during forward bias of a P-N junction?
    • A) Reverse current increases
    • B) Majority carriers decrease
    • C) Minority carriers flow across the junction
    • D) Mobile charges accumulate around the junction
    • Answer: C) Minority carriers flow across the junction
  • What is the symbol for a P-N junction?
    • A) +-
    • B) |-
    • C) -|
    • D) |+
    • Answer: D) |+
  • Which scientist is credited with the exploration of P-N junctions?
    • A) Albert Einstein
    • B) Isaac Newton
    • C) Russel Ohi
    • D) Marie Curie
    • Answer: C) Russel Ohi
  • What is the basic building block of all electronic devices?
    • A) Capacitor
    • B) Resistor
    • C) Diode
    • D) Transistor
    • Answer: C) Diode
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Summary

In conclusion, the P-N junction serves as a fundamental component in semiconductor technology, forming the basis for various electronic devices.

Through the controlled combination of n-type and p-type semiconductors, P-N junctions enable the flow of electrons and holes, crucial for the operation of diodes, transistors, solar cells, and more. Understanding the behavior of P-N junctions, including their depletion regions and biasing techniques, is essential for designing and utilizing electronic circuits effectively.

With applications ranging from computers to amplifiers, the significance of P-N junctions in modern technology cannot be overstated.