How does the number of charge carriers affect a semiconductor’s conductivity?

The electrical conductivity of a semiconductor is directly dependent on the number of charge carriers—specifically free electrons and holes—present per unit volume, as well as the rate at which these carriers move under the influence of an electric field.12

In an intrinsic (pure) semiconductor, conductivity is relatively low at room temperature because the number of available charge carriers is limited by thermal energy. To increase conductivity, a process called doping is used to intentionally introduce impurities into the crystal structure.12

• n-type semiconductors: Doping with pentavalent atoms (such as arsenic) donates extra electrons to the conduction band, increasing the number of negative charge carriers.12
• p-type semiconductors: Doping with trivalent atoms (such as boron) creates additional holes in the valence band, increasing the number of positive charge carriers.12

By increasing the concentration of these carriers, the material's ability to conduct electricity is significantly enhanced, despite a potential decrease in carrier mobility.12