Question

In an unbiased p-n junction, at equilibrium, which of the following statements is true?

Options

• Diffusion current is zero but drift current exists.

• Diffusion current exists but drift current is zero.

• Diffusion and drift currents are equal and opposite.

• Both the diffusion and drift currents exist but are unequal.

Answer 1

Diffusion and drift currents are equal and opposite.

Explanation:

Electrons initially diffuse from the n-side to the p-side, while holes migrate from the p-side to the n-side. This diffusion results in a depletion region and an internal electric field. The electric field induces the movement of carriers in the opposite direction.

At equilibrium:

`I_"diffusion" = I_"drift"`

But they flow in opposite directions, so the total current becomes zero.

Hence, Diffusion and drift currents are equal and opposite.