N-type and P-type semiconductors

2 min read

N-type and P-type semiconductors are two types of semiconductors that have been doped with impurities to alter their electrical conductivity. Doping is the process of adding impurities to a pure semiconductor material to create an excess or deficiency of free charge carriers.

N-type semiconductors are doped with impurities from Group V of the periodic table, such as phosphorus or arsenic. These impurities have five valence electrons, one more than the four valence electrons of the semiconductor atoms. When the impurity atoms are added to the semiconductor, they bond with four of the semiconductor atoms, but the fifth valence electron is not involved in the bonding and is free to move around the semiconductor material. These free electrons are the majority of charge carriers in n-type semiconductors.

P-type semiconductors are doped with impurities from Group III of the periodic table, such as boron or indium. These impurities have three valence electrons, one less than the four valence electrons of the semiconductor atoms. When the impurity atoms are added to the semiconductor, they bond with three of the semiconductor atoms, but the fourth valence electron is missing and creates a hole. Holes are vacancies in the valence band of the semiconductor, and they can act as positive charge carriers. Holes are the majority of charge carriers in p-type semiconductors.

Working of N-type and P-type semiconductors

N-type and p-type semiconductors can be used to create a variety of electronic devices, such as diodes, transistors, and integrated circuits. These devices work by controlling the flow of current through the semiconductor material.

For example, a diode is a semiconductor device that allows current to flow in one direction but not the other. This is because diodes have a p-n junction, which is a boundary between a p-type semiconductor and an n-type semiconductor. When a voltage is applied to the diode in the forward direction, the holes in the p-type semiconductor are attracted to the electrons in the n-type semiconductor. This creates a current flow across the junction. However, when a voltage is applied to the diode in the reverse direction, the holes in the p-type semiconductor are repelled by the electrons in the n-type semiconductor. This prevents current from flowing across the junction.

Transistors are another type of semiconductor device that is used to control the flow of current. Transistors have three terminals: the collector, the emitter, and the base. The collector and emitter terminals are made of n-type semiconductor, and the base terminal is made of p-type semiconductor. A small current flowing through the base terminal can control the flow of a much larger current flowing between the collector and emitter terminals.

Integrated circuits (ICs) are complex electronic devices that contain millions or even billions of transistors and other semiconductor components. ICs are used in a wide variety of electronic devices, such as computers, smartphones, and televisions.

Applications of N-type and P-type semiconductors

N-type and p-type semiconductors are used in a wide variety of electronic devices, including:

  • Diodes (rectifiers, LEDs, photodiodes, etc.)

  • Transistors (BJTs, MOSFETs, FETs, etc.)

  • Integrated circuits (microprocessors, memory chips, etc.)

  • Solar cells

  • Light-emitting diodes (LEDs)

  • Laser diodes

  • Sensors

  • Photodetectors

  • Power electronics devices (thyristors, GTOs, IGBTs, etc.)

N-type and p-type semiconductors are essential components of modern electronics. They are used in a wide variety of devices, from simple diodes to complex integrated circuits.