Page "Semiconductor" Paragraph 52

The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped.

In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors.

A donor atom that activates ( that is, becomes incorporated into the crystal lattice ) donates weakly bound valence electrons to the material, creating excess negative charge carriers.

These weakly bound electrons can move about in the crystal lattice relatively freely and can facilitate conduction in the presence of an electric field.

( The donor atoms introduce some states under, but very close to the conduction band edge.

Electrons at these states can be easily excited to the conduction band, becoming free electrons, at room temperature.

) Conversely, an activated acceptor produces a hole.

Semiconductors doped with donor impurities are called n-type, while those doped with acceptor impurities are known as p-type.

The n and p type designations indicate which charge carrier acts as the material's majority carrier.

The opposite carrier is called the minority carrier, which exists due to thermal excitation at a much lower concentration compared to the majority carrier.