semiconductor, Class of crystalline solids with electrical conductivity between that of a conductor and an insulator. Such materials can be treated chemically to allow transmission and control of an electric current. Semiconductors are used in the manufacture of electronic devices such as diodes, transistors, and integrated circuits. Intrinsic semiconductors have a high degree of chemical purity, but their conductivity is poor. Extrinsic semiconductors contain impurities that produce much greater conductivity. Some common intrinsic semiconductors are single crystals of silicon, germanium, and gallium arsenide; such materials can be converted into the technologically more important extrinsic semiconductors by addition of small amounts of impurities, a process called doping (see dopant). Advances in semiconductor technology in recent years have gone hand in hand with increased operational speed in computers.