ndoped

Ndoped, more commonly written as n-doped or n-type doping, refers to the intentional introduction of donor impurities into a semiconductor to increase its electron concentration. Donor atoms have one more valence electron than the host lattice; when they substitute for host atoms they donate electrons to the conduction band, producing mobile electrons as majority carriers. The donor energy level lies close to the conduction band, so at typical temperatures most dopants are ionized, and the electron concentration greatly exceeds the hole concentration.

Common donor elements include phosphorus, arsenic, and antimony in silicon, and phosphorus or arsenic in germanium; in compound semiconductors such as gallium arsenide, donors can also act as shallow donors. The presence of donors shifts the Fermi level toward the conduction band and increases electrical conductivity, enabling n-type conduction where electrons are the dominant carriers.

Doping concentrations typically range from about 1×10^14 to 1×10^20 atoms per cubic centimeter, with higher levels approaching degenerate doping, where the material starts to behave more like a metal. Heavy doping can reduce carrier mobility through impurity scattering and can cause band gap narrowing.

Doping is achieved by diffusion, ion implantation, or during crystal growth and epitaxy (for example, chemical vapor deposition or molecular beam epitaxy). N-doped layers form the basis of many electronic devices, including diodes and transistors, and are often used in conjunction with p-doped regions to form p-n junctions. The term n-doped is contrasted with p-doped materials, which use acceptor impurities to create holes as majority carriers.