Ndoping

N-doping, or n-type doping, is the process of introducing donor impurities into a semiconductor to increase the number of free electrons, producing an n-type material in which electrons are the majority charge carriers. This modification alters the electronic structure so that electrons dominate conduction.

Donor atoms, such as phosphorus, arsenic, or antimony in silicon, have more valence electrons than the host lattice and introduce energy levels just below the conduction band. At practical temperatures, these donor levels ionize, releasing electrons into the conduction band and leaving positively charged donor ions behind. The result is enhanced electrical conductivity with electrons as the primary carriers.

Common dopants include phosphorus, arsenic, and antimony for silicon; other materials use different donor species. Doping can be achieved by diffusion or by ion implantation, often followed by annealing to activate dopants and repair lattice damage. Precise control of dopant depth and concentration is essential for device performance.

Doping concentrations typically range from about 10^14 to 10^20 atoms per cubic centimeter, depending on the application. Higher concentrations can lead to degeneracy, where the Fermi level approaches or enters the conduction band and carrier mobility is reduced due to impurity scattering.

Applications include forming n-type regions in diodes and transistors, creating source and drain regions in MOSFETs, and tailoring junction properties in semiconductor devices. N-doping is commonly contrasted with p-doping, which uses acceptor impurities to create holes as the majority carriers; boron in silicon is a classic p-type dopant.

Challenges in n-doping include achieving precise dopant distribution, maximizing activation efficiency, minimizing lattice damage from implantation, and avoiding unintended compensating impurities, all critical for nanoscale device fabrication.