Difference between drift current and diffusion current

Drift current

Diffusion current

Under the action of electric field the charge carriers in the semiconductor material stops moving randomly and start drifting towards or
away the applied electric field depends upon their nature. This drift of charge carriers produces drift current.
In semiconductor there may arise a situation where the concentration of charge carriers within the crystal becomes different and hence
producing concentration gradient, due to which charge carriers cross the surface to maintain equilibrium and constitute a current which is
known as diffusion current.
For drift current external electric field is essential. For diffusion current external field is not required any external energy may stimulate this process.
It depends on carrier concentration and external electric field. It depends upon rate of charge of carrier concentration per unit length.

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