Electrical conductivity is the ability to conduct electrical current under the application of a voltage, and it is defined as the ratio of the electric current density to the electric field in a material. A semiconductor is a material whose electrical conductivity lies between that of a typical conductor, like copper, and that of a typical insulator, like rubber. Semiconducting properties are usually strongly temperature-dependent. Although most common semiconductors are of a solid, crystalline material, some semiconductors are also found in liquid and amorphous states (an amorphous state lacks a distinct crystalline structure). Semiconductors commonly produced include the chemical elements silicon, germanium, diamond (carbon), tellurium, boron, and selenium, and the chemical compounds gallium arsenide, zinc selenide, and lead telluride.

The sign of the majority of its charged carriers—i.e., its electrons—normally indicates the classification of a semiconductor. Therefore, a semiconductor with an excess number...