How do p-n junctions make diodes possible?

A p-n junction makes a diode possible by acting as a rectifier, allowing electrical current to flow in only one direction.123

This functionality arises from the interaction between p-type and n-type semiconductor materials:

• Depletion Layer: At the interface of the two materials, electrons from the n-side diffuse to fill holes on the p-side, creating a depletion layer that acts as an insulator, preventing further current flow under normal conditions.23
• Forward Bias: When a positive voltage is applied to the p-side, the barrier is overcome, allowing majority charge carriers to cross the junction and enabling a large current to flow.145
• Reverse Bias: When a positive voltage is applied to the n-side (or negative to the p-side), the depletion region widens, effectively blocking the flow of current.123

Because of this ability to permit current in only one direction, p-n junctions serve as the essential building blocks for diodes, which are fundamental components in semiconductor devices and electronic circuits.143