What is a semiconductor?

Semiconductors are an essential part of today’s electronics and information technology sectors as it is used in thousands of modern devices. Here we take a look at the semiconductor definition. 

What does a semiconductor mean? A semiconductor refers to a solid material that may conduct electricity more than an insulator, such as dry wood, plastic, dry cotton, rubber and glass, but less than pure conductors like iron, copper, silver, brass, or gold. 

A conductor is a material that allows electricity to pass through it, while an insulator does not.

Semiconductors are widely used as key materials in computers and other electronic devices. Some examples of semiconductors are germanium, gallium arsenide and silicon.

Different type of a semiconductor explained

Semiconductors can be broadly classified as intrinsic and extrinsic. 

• Intrinsic semiconductors 

Intrinsic semiconductors are made out of pure chemicals free of impurities. According to the energy band theory, the conductivity of an intrinsic semiconductor will be zero at the ambient temperature. Silicon and germanium are intrinsic semiconductors.

• Extrinsic semiconductors

Extrinsic semiconductors have been mixed with impurities in regulated amounts to ensure that they are conductive. These semiconductors can be either n-type (negative) or p-type (positive). The process of mixing impurities into intrinsic semiconductors is known as doping. 

The kind of impurities introduced to intrinsic semiconductors are determined by the type of semiconductor. The density of electrons in an extrinsic semiconductor is not equal to the density of electrons.

Extrinsic semiconductors examples are silicon and germanium doped with aluminium, indium, phosphorus and arsenic. 

How does a semiconductor work?

The operation of a semiconductor occurs at the level of atoms and electrons, and how these operate within an atom. The basic functionality of an electron lies as they arrange themselves in layers known as shells inside an atom. 

The outermost shell in the atom is called a valence shell, and the electrons in this shell establish covalent bonds with the atoms around its own atoms. A covalent bond can be defined as a chemical bond that consists of shared electron pairs between atoms.

If the neighbouring atoms carry the same valence, electrons may establish bonds with the valence electrons of these atoms. To attain this, atoms cluster themselves into crystal structures.