When a P-N junction is reverse-biased, the external voltage applies in a direction opposite to the normal flow of current through the diode. In this condition, the negative terminal of the external voltage source connects to the p-type region of the diode, while the positive terminal connects to the n-type region.
The reverse biasing of a P-N junction increases the potential barrier at the junction. This barrier hinders the crossing of majority carriers (electrons in the n-region and holes in the p-region) through the junction and the subsequent flow of current through the diode. Consequently, only a small leakage current, known as reverse saturation current, flows through the diode.