Biasing metal and n-type semiconductor junctions involves applying a voltage to metal while grounding the semiconductor. The resulting current is positive when it flows from the metal to the semiconductor.

For Schottky junctions, applying a positive voltage lowers the metal's Fermi level, reducing the barrier for electrons in the semiconductor and enabling net electron flow from the semiconductor to the metal. This results in a rapidly increasing forward bias current.

Conversely, negative voltage raises the metals' Fermi level, blocking electron flow from the semiconductor to the metal. However, some electrons overcome the junction barrier, leading to a small reverse bias current.

For ohmic junctions, even a small positive voltage triggers a large forward bias current due to the absence of any barrier. Under reverse biasing, a small barrier exists for electron flow from the metal to the semiconductor, which disappears if the reverse bias exceeds a few tenths of a volt.

The behavior is reversed for contacts formed with metal and p-type semiconductors.

Biasing metal-semiconductor junctions enables control over current flow, which is essential in devices like diodes, transistors, and photovoltaic cells.