Chargecarrying

Chargecarrying refers to the transport of electric charge through a material or medium by mobile charged particles, known as charge carriers. The charge carried can be negative or positive and the motion of these carriers constitutes electric current. The identity of the carriers depends on the medium: electrons are predominant in metals and many semiconductors, holes (the absence of an electron) act as positive carriers in p-type semiconductors, and ions carry charge in electrolytes and ionic conductors. In plasmas, ions and electrons both contribute.

In solids, the effectiveness of charge carrying is described by carrier density, charge, and mobility. Mobility, defined as drift velocity per unit electric field, measures how easily carriers move in an applied field. Conductivity is the result of the combined contributions of all carrier types: σ = q(nμn + pμp) in a two-carrier semiconductor, where n and p are electron and hole densities, μn and μp their mobilities. In metals, the high density of conduction electrons leads to high conductivity and rapid charge carrying; in electrolytes, ionic motion under an electric field carries current, and temperature, concentration, and viscosity influence mobility.

Charge carrying underpins electrical conduction, electronic devices, energy storage, and electrochemical processes. It can occur through drift under an electric field and through diffusion due to concentration gradients. In many devices, control of charge carrying is achieved by material design, doping, interfaces, and microstructure, affecting carrier density and mobility.