What are semiconductors and how do they work?

Semiconductors are a class of materials with electrical conductivity between that of a conductor (like metals) and an insulator (like glass). They play a crucial role in modern electronics, enabling devices like transistors, solar cells, and integrated circuits.

Semiconductors work by allowing or restricting the flow of electric charge carriers (electrons or holes) through a material. This is determined by the material's energy band structure and the presence of impurities (doping).

In their pure state, semiconductors have four electrons in their outer shell, which are free to move and conduct electricity. However, when an electric field is applied, these electrons can move easily, making the material conductive.

Semiconductors can be made more conductive by adding impurities (doping). This introduces extra electrons (n-type) or holes (p-type) that can carry charge. These doped semiconductors are called extrinsic semiconductors, and they are the basis for many electronic devices.

The most common semiconductor is silicon (Si), which is used in most electronic devices today. Other semiconductors include germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP).