The drift current in a p-n junction diode is
This question has multiple correct options
A. motion of charge carriers due to the electric field
B. motion of charge carriers due to the charge concentration gradient
C. in same direction as the diffusion current
D. opposite in the direction to the diffusion current

Hint: Define drift current and the diffusion current of a p-n junction diode. The drift current is due to charge flow because of the electric field. Diffusion current is due to the flow of charge because of the concentration gradient. Find the similarities and the dissimilarities of the two quantities.

Complete step by step answer:
A p-n junction diode is formed when a p-type semiconductor is fused with an n-type semiconductor.
The diffusion current inside a conductor is the current due to the flow of charge carriers inside the diode due to the concentration gradient of the charge carriers. So, we can say that the diffusion current is due to the flow of the charge carriers from a higher concentration region to a lower concentration region. A higher concentration region means that the concentration of electrons is high at that region and a lower concentration region means that the concentration of electrons is low at that region.
The drift current in a semiconductor can be defined as the current produced due to the flow of charge carriers inside the diode due to the presence of the electric field. As we apply the voltage to the diode, the holes will move towards the negative terminal of the battery and the electrons will move towards the positive terminal of the battery. The direction of the drift current is opposite to the direction of the diffusion current.
So, we can say that the correct options are (A) and (D).

Note:
We have a few differences between the drift current and the diffusion current. The drift current obeys the ohm’s law and the diffusion current obeys the Fick’s law. The drift current depends on the permittivity of the medium while the diffusion current does not depend on the permittivity of the medium.