fieldeffect

Field effect, also known as fieldeffect, is the modulation of a material's electrical properties by an external electric field. In semiconductors, applying a voltage to a gate electrode changes the carrier concentration near an interface, creating depletion or accumulation layers that alter conductance. The field effect is a foundational principle for modern solid-state electronics.

A field-effect transistor (FET) uses the field effect to control current between source and drain terminals. The gate is separated from the conducting channel by a dielectric or by a reverse-biased junction, enabling voltage-controlled current with high input impedance. The device operates in regions such as cutoff, triode (linear), and saturation, depending on gate and drain voltages.

Common FET types include metal-oxide-semiconductor FETs (MOSFETs), which use a thin oxide dielectric; junction FETs (JFETs), which rely on a depletion region formed by a p–n junction; and other variants like MESFETs and FinFETs. MOSFETs dominate contemporary integrated circuits due to scalability, low leakage, and fast switching.

Field-effect science and devices underpin digital logic, analog amplifiers, and radio-frequency circuits. The name field effect also guides studies of surface physics, oxide-electrolyte interfaces, and electrostatic gating in nanoscale systems.