Why does a semiconductor diode conduct mainly in one direction?

A semiconductor diode conducts electricity in only one direction because of the properties of its p-n junction, which is formed by joining p-type and n-type materials.12

At the interface of these materials, a depletion layer forms, acting as an insulator that prevents the flow of charge carriers. The diode's behavior depends on the applied voltage:34

• Forward Bias: When a positive voltage is applied to the p-side, it repels holes toward the junction, while a negative voltage on the n-side repels electrons toward the junction. This allows majority charge carriers to cross the barrier, creating a significant electric current.23
• Reverse Bias: When the voltage is reversed, the charge carriers are attracted away from the junction. This widens the depletion layer and effectively blocks current flow, allowing only a negligible leakage current.254

This process, known as rectification, is fundamental to converting alternating current to direct current.2