Question

When a P-N junction diode is reverse biased (A) height of the potential barriers decreases (B) no change in the current takes place (C) electrons and holes move away from the junction deflection region. (D) electrons and holes one attracted towards each other and move towards the deflection region.

Short answer

In a reverse-biased PN junction diode, electrons and holes move away from the junction deflection region. Therefore, the correct answer is (C).

Step-by-step solution

Define PN Junction Diode

A PN junction diode is a semiconductor device formed by the junction of a p-type semiconductor (holes as majority carriers) and an n-type semiconductor (electrons as majority carriers). It is important to understand the role of majority and minority carriers in the operation of the diode.

Define Reverse Bias

Reverse bias is a condition when the voltage applied to a PN junction diode is in such a way that it opposes the flow of current through the diode. In a reverse bias connection, the positive terminal of the voltage source is connected to the n-side and the negative terminal is connected to the p-side of the diode. Now, let's analyze the given answer choices based on the effects of a reverse-biased diode.

Analyze Answer Choice A

When a PN junction diode is reverse biased, the height of the potential barrier actually increases. The applied reverse voltage adds up to the potential barrier, which prevents the majority carriers to cross the junction. Therefore, answer choice A is incorrect.

Analyze Answer Choice B

When the diode is reverse biased, there is indeed a change in the current; a tiny reverse saturation current (composed mainly of minority carriers) flows through the diode. This current is very small in comparison to the forward current. So, answer choice B is also incorrect.

Analyze Answer Choice C

In reverse bias, the electric field created by the applied voltage tends to move the electrons and holes away from the junction deflection region. The majority carriers move away from the junction, thereby widening the depletion region which means answer choice C is correct.

Analyze Answer Choice D

Since the applied voltage in reverse bias opposes the flow of majority carriers across the junction, the electrons and holes are not attracted towards each other, and they move away from the deflection region. So, answer choice D is incorrect. So, based on our analysis of a reverse-biased PN junction diode, the correct answer is: \(C) \text{ Electrons and holes move away from the junction deflection region}\).