What is the Difference Between Diffusion Current and Drift Current?

The main difference between diffusion current and drift current lies in their causes and directions. Here is a comparison of the two types of currents:

Diffusion Current:

Caused by the diffusion of charge carriers (electrons and holes) in a semiconductor material due to a concentration gradient.
Direction depends on the slope of the carrier concentration.
Obeys Fick's law: $$J=-qD\frac{d\rho}{dx}$$.
Occurs in junction diodes or semiconductor devices.
The primary carrier concentrations define the diffusion current's direction.

Drift Current:

Caused by the motion of charge carriers due to the force exerted on them by an electric field.
Direction is always in the direction of the electric field.
Obeys Ohm's law.
Found in all conducting materials where the current flows as the flow of electrons.
The drift current follows Ohm's law and is mainly influenced by the external field and charge carrier concentrations.

In summary, diffusion current is caused by the diffusion of charge carriers in response to a concentration gradient, while drift current is caused by the motion of charge carriers under the influence of an electric field. The direction of the diffusion current depends on the slope of the carrier concentration, whereas the drift current always flows in the direction of the electric field.

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What is the Difference Between Diffusion Current and Drift Current?

Comparative Table: Diffusion Current vs Drift Current

Here is a table comparing the differences between diffusion current and drift current:

Diffusion Current	Drift Current
Occurs due to the motion of charge carriers from higher concentration to lower concentration	Occurs due to the movement of charge carriers in response to an applied electric field
Does not require an external electric field	Requires an external electric field
Depends primarily on the repulsive forces between carriers	Depends on the external field and charge carrier mobility
Direction of the current flow is determined by the concentration gradient	Direction of the current flow is determined by the electric field
flow of holes and electrons are in the same direction as the concentration gradient	Positive carriers or holes flow in the same direction as the electric field, while negative carriers or electrons flow in the reverse direction
Net movement of charged particles creates a diffusion current	Net movement of charged particles creates a drift current

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.