Question

The dominant mechanisms for motion of charge carriers in forward and reverse biased silicon $p-n$ junctions are

• A. Drift in forward bias, diffusion in reverse bias
• B. Diffusion in forward bias, drift in reverse bias
• C. Diffusion in both forward and reverse bias
• D. Drift in both forward and reverse bias

Answer 1

Answer: (B)

In the forward biased mode, we apply voltage in a direction opposite to that of barrier potential, that is, p-side to the positive terminal and n-side to the negative terminal of the battery. Thus, electrons in the n-side, holes in the p-side are pushed towards the junction which results in increased diffusion.
In reverse biased mode, we apply voltage in a direction of that of barrier potential. The electrons in n-side, holes in p-side pushed away from the junction that results in the drift current.