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Drift Current

Drift current is the current that is a result of an applied electric field.

Overview[edit]

The drift current is the net charge of all the charge carrier at the carrier drift velocity. The drift velocity is defined as

Equation v Subscript d Baseline equals mu Subscript n comma p Baseline upper E

There are Equation n free electrons per cubic meter of this material, each with have an elementary charge Equation q .

Drift current density Equation upper J Subscript n Superscript drift due to free electrons

Equation upper J Subscript n Superscript drift Baseline equals minus q n v Subscript d n Baseline equals q n mu Subscript n Baseline upper E

While the current density Equation upper J Subscript p Superscript drift due to holes is

Equation upper J Subscript p Superscript drift Baseline equals q p v Subscript d p Baseline equals q p mu Subscript p Baseline upper E

The total drift current density is the sum of the two drift current densities.

Equation StartLayout 1st Row 1st Column upper J Superscript drift 2nd Column equals upper J Subscript n Superscript drift Baseline plus upper J Subscript p Superscript drift Baseline 2nd Row 1st Column Blank 2nd Column equals q n mu Subscript n Baseline upper E plus q n mu Subscript p Baseline upper E 3rd Row 1st Column Blank 2nd Column equals q left-parenthesis n mu Subscript n Baseline plus p mu Subscript p Baseline right-parenthesis upper E EndLayout

Where the conductivity Equation sigma is

Equation sigma equals q left-parenthesis n mu Subscript n Baseline plus p mu Subscript p Baseline right-parenthesis

which is the generalized form of Ohm's law.

Equation upper J equals sigma upper E equals StartFraction upper E Over rho EndFraction

Where Equation sigma is the conductivity [1/Ωcm] and Equation rho is the resistivity [Ωcm].

Diffusion vs Drift currents[edit]

See also: diffusion current
Diffusion current Drift current
Result of Having mass Having charge
Due to Carrier movement due to concentration gradient Carrier movement due to electric field applying a force
Obey Fick's law Ohm's law

See also[edit]

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