Question

When \(\mathrm{P}-\mathrm{N}\) junction diode is forward based, then (A) Both the depletion region and barrier height are reduced. (B) Both depletion region and barrier height are increased. (C) The deflection region is winded and barrier height is reduced. (D) The depletion region is reduced and barrier height is increased.

Short answer

When a P-N junction diode is forward biased, both the depletion region and barrier height are reduced. Therefore, the correct answer is (A) Both the depletion region and barrier height are reduced.

Step-by-step solution

1. Understanding the P-N junction and forward bias

: A P-N junction diode is a two-terminal semiconductor device made of a P-type (holes are the majority carriers) and N-type (electrons are majority carriers) semiconductor material joined together. When no voltage is applied, the P-N junction has a natural potential barrier called the "built-in potential" that prevents the charge carriers (electrons and holes) from recombining across the junction. Forward biasing a P-N junction diode means connecting the positive terminal of an external voltage supply to the P-side of the diode and the negative terminal to the N-side. In this condition, the applied voltage opposes the built-in potential barrier, allowing the charge carriers to flow across the junction easily.

2. Depletion region and barrier height under forward bias

: When a P-N junction diode is under forward bias, the applied voltage reduces the built-in potential barrier. Consequently, the junction becomes more accessible for the charge carriers to flow across, and the net current increases. During this process, the depletion region, which is a region of immobile charged particles (such as ions) formed near the junction, also becomes thinner. Therefore, forward biasing causes a reduction in the depletion region as well as the barrier height.

3. Selecting the correct option

: From our analysis, we found that when a P-N junction diode is forward biased, both the depletion region and barrier height are reduced. Hence, the correct option is: (A) Both the depletion region and barrier height are reduced.