dopantene

Dopants are impurities intentionally introduced into a material to modify its electrical, optical, mechanical, or chemical properties. In solid-state physics, doping is most common in semiconductors, where small concentrations of donor or acceptor species change the number of charge carriers. In silicon, common donors are phosphorus and arsenic; acceptors include boron and aluminium. Donors provide extra electrons (n-type), while acceptors create holes (p-type). The dopant atoms replace host lattice atoms in substitutional sites or occupy interstitial sites, depending on size and valence.

Dopant concentration ranges from about 10^14 to 10^20 cm^-3, depending on device requirements. High dopant levels can cause impurity scattering, lattice strain, and activation limitations. Activation refers to the fraction of dopant atoms that occupy electrically active sites after processing, often requiring annealing.

Doping methods include diffusion, ion implantation, and in-situ incorporation during crystal growth. Diffusion uses high temperature to drive dopants from a surface into the material; ion implantation injects ions with control over depth and dose but may require annealing to repair lattice damage. In-situ doping during crystal growth can incorporate dopants as the material forms, offering precise control of distribution.

In optoelectronic materials, dopants such as rare earth ions (for example erbium and europium) introduce optical transitions for lasers and amplifiers. Other fields use doping to alter properties of metal oxides, polymers, glass, and ceramics. In solar cells, LEDs, and transistors, doping underpins junction formation and tailored electronic structure.