Question

differentiate between drift current and diffusion current.

Answer 1

Diffusion current :
Diffusion current occurs even though there isn't an electric field applied to the semiconductor.
It depends on constants Dp and Dn, and +q and −q, for holes and electrons respectively but it is independent of permittivity.
Direction of the diffusion current depends on the change in the carrier concentrations, not the concentrations themselves.
Drift current:
Drift current depends on the electric field applied on the p-n junction diode.
It depends upon permittivity.
Direction of the drift current depends on the polarity of the applied field.