Question

When p-n junction is reverse biased (A) no current flows (B) majority carriers move towards the junction (C) minority carriers move towards the junction (D) both majority and minority carriers move away from the junction

Short answer

In a reverse biased p-n junction, the minority carriers (electrons in the p-side and holes in the n-side) move towards the junction. So, the correct answer is (C) minority carriers move towards the junction.

Step-by-step solution

Understanding p-n junction

A p-n junction is formed when a p-type semiconducting material, which has majority carriers as holes, is joined with an n-type semiconducting material, which has majority carriers as electrons.

Reverse bias

A p-n junction is said to be reverse biased when the voltage is applied in such a way that the potential barrier at the junction increases. In this case, the positive terminal of the battery is connected to the n-type material, and the negative terminal is connected to the p-type material.

Majority and minority carriers

Majority carriers are the dominant charge carriers in a semiconducting material. In a p-type material, holes are the majority carriers, while in an n-type material, electrons are the majority carriers. Minority carriers are the less-dominant charge carriers in a semiconducting material. Electrons are minority carriers in p-type material, and holes are minority carriers in n-type material.

Carrier movement in reverse biased p-n junction

When a p-n junction is reverse biased, the potential barrier increases. This effectively discourages majority carriers (holes in the p-side and electrons in the n-side) from moving across the junction. So, they move away from the junction. On the other hand, the minority carriers (electrons in the p-side and holes in the n-side) get attracted to the respective battery terminals, and thus they move towards the junction. Based on the analysis, the correct answer is: (C) minority carriers move towards the junction