semiconducting

Semiconducting materials are those whose electrical conductivity lies between that of metals and insulators. They include elemental materials such as silicon and germanium, and compound materials such as gallium arsenide, indium phosphide, and cadmium telluride. The electrical behavior of semiconductors is largely governed by a band gap between the valence and conduction bands. At absolute zero, a pure intrinsic semiconductor acts as an insulator; thermal energy or impurities generate charge carriers that enable conduction.

Doping introduces impurities to tailor conductivity. In n-type semiconductors, donor atoms supply extra electrons, increasing negative carriers; in p-type semiconductors, acceptor atoms create holes as majority carriers. The combination of p-type and n-type regions creates p–n junctions, which form diodes and constitute the fundamental active element of most electronics. Charge transport depends on carrier concentration and mobility, with electrons typically more mobile than holes.

Temperature and light can modulate semiconducting properties. In intrinsic materials, conductivity rises with temperature due to thermally generated carriers; in doped materials, the response depends on impurity levels and operating conditions. At low temperatures, conduction can be limited by dopant freeze-out, while at higher temperatures intrinsic conduction may become significant.

Applications span electronics, photovoltaics, and optoelectronics. Silicon dominates integrated circuits and solar cells, in part due to mature fabrication, the native oxide that serves as an insulator, and favorable material properties. Other semiconductors are used for high-speed electronics (such as GaAs), power electronics, LEDs, and detectors. Ongoing research in semiconducting materials focuses on band-gap engineering, nanostructures, and new compounds to improve performance and efficiency.