Doping

For a semiconductor material to have the properties needed to work in electronic components, impurities are usually added. The impurities cause the material to conduct currents in certain ways. The addition of an impurity to a semiconductor is called doping. Sometimes the impurity is called a dopant.

Donor impurities

When an impurity contains an excess of electrons, the dopant is called a donor impurity. Adding such a substance causes conduction mainly by means of electron flow, as in a metal like copper. The excess electrons are passed from atom to atom when a voltage exists across the material. Elements that serve as donor impurities include antimony, arsenic, bismuth, and phosphorus. A material with a donor impurity is called an N type semiconductor, because electrons have negative charge.

Acceptor impurities

If an impurity has a deficiency of electrons, the dopant is called an acceptor impurity. When a substance such as aluminum, boron, gallium, or indium is added to a semiconductor, the material conducts by means of hole flow. A hole is a missing electron; it is described in more detail shortly.
A material with an acceptor impurity is called a P-type semiconductor, because holes have positive charge.