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Semiconductors are used everywhere in the modern world. They have literally thousands of applications including controlling the engine management systems in cars, the navigation systems of aircraft and even the function of the white goods in our kitchens.

What makes semiconductors so special and what do they do?

The term 'semi-conductor' is a generic term referring to materials which offer electrical conductivity greater than that of an insulator but not as much as that of a conductor. In the electronics manufacturing sector, semiconductors are sometimes known as Integrated Circuits (ICs) or Silicon Chips.

The conductivity of semiconductors can be controlled with electric currents, electromagnetic fields and light energy. This makes it possible to design and manufacture electronic components from semiconductors that can amplify, switch, convert sunlight to electricity or even produce light from electricity.

Why do semiconductors have different properties?

Semiconductors are commonly made from the element silicon which has a diamond like network lattice where each silicon atom is bonded to four other silicon atoms. Each Silicon atom has four valence electrons that are used in bonding of the network lattice.

In electronics, the usefulness of semiconductors is derived from the fact that impurities introduced to the semiconductor lattice structure can dramatically alter their conductivity.

For example, the addition of very small traces of certain impurities to either silicon or germanium enhances the conductivity of these materials and produces what is known as extrinsic (or impurity semiconductors). For example, if the element Boron is added to the Silicon lattice it disrupts the lattice equilibrium because it has only three valence electrons and can only form three of the required four bonds for the perfect lattice, creating an electron vacancy or hole. Electrons from nearby bonds may move into this vacancy but in doing so leave behind a vacancy in their previous position. In this way electrons move through the structure and the 'holes' move in the opposite direction to the electrons.

This type of semiconductor in which holes enable electron movement is called a p type semiconductor where p stands for positive.

If other impurities are added to Silicon such as Arsenic, Bismuth or Antimony which each have five valence electrons, a second type of extrinsic semiconductor is produced known as an n-type, where n stands for negative.

The fifth or extra electron is not required by the crystal lattice and is free to move through the structure to function as a conduction electron. Semiconductors or Integrated circuits are available in a variety of forms, each carrying out specific tasks. Some of the more common ones are listed below.

Semiconductors Topics



Diodes and Transistors

Memory Chips or Modules

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Guide Written by Paul Wilson

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