What happens to the potential barrier of the p- n junction diode when it is?

The potential barrier of a p-n junction diode can change under different conditions. Here are a few scenarios:

Forward bias: When a positive voltage is applied to the p-type region and a negative voltage is applied to the n-type region (i.e., the p-side is at a higher potential than the n-side), the potential barrier reduces. This reduction in the potential barrier allows the majority charge carriers (holes in the p-region and electrons in the n-region) to move across the junction, facilitating current flow through the diode.

Reverse bias: When a negative voltage is applied to the p-type region and a positive voltage is applied to the n-type region (i.e., the p-side is at a lower potential than the n-side), the potential barrier increases. This increased potential barrier prevents the majority charge carriers from easily crossing the junction, resulting in minimal current flow through the diode. In this state, the diode is said to be in the reverse-biased condition.

It's important to note that the potential barrier is an inherent property of the p-n junction diode based on the different doping levels of the p and n regions. The applied bias alters the effective potential barrier, allowing or hindering the flow of charge carriers.