material that has electrical conductivity intermediate to that of a conductor and an insulator / From Wikipedia, the free encyclopedia

A semiconductor is a material that in some cases will conduct electricity but not in others.[1] Good electrical conductors, like copper or silver, easily allow electricity to flow through them.[2] Materials that block the flow of electricity, like rubber or plastic, are called insulators.[2] Insulators are often used to protect people from electric shock. As the name implies, a semiconductor does not conduct as well as a conductor.[3] Silicon is the most used semiconductor, but gallium arsenide is also used.

Semiconductor-based electronic components

By the addition of different atoms into the crystal lattice (grid) of the semiconductor it changes its conductivity by making n-type and p-type semiconductors. Silicon is the most important commercial semiconductor, though many others are used. They can be made into transistors, which are small amplifiers. Transistors are used in computers, mobile phones, digital audio players and many other electronic devices.

Like other solids, the electrons in semiconductors can have energies only within certain bands (i.e. ranges of energy levels) between the energy of the ground state, corresponding to electrons tightly bound to the atomic nuclei of the material, and the free electron energy, which is the energy required for an electron to escape entirely from the material.