Metal–semiconductor junction

A metal–semiconductor junction is an interface between a metal and a semiconductor. Its electrical behavior depends on the interfacial energy barrier, material properties, and contact structure.

Schottky barrier: An energy barrier that forms for charge carriers at a metal–semiconductor interface. It governs carrier injection and gives many metal–semiconductor contacts their rectifying behavior.
Work function: The energy required to remove an electron from a material’s Fermi level to vacuum. The metal work function enters ideal estimates of the junction barrier.
Ohmic contact: An electrical contact with approximately linear, nonrectifying current–voltage behavior. It is the desired alternative when a metal contact should pass current in either direction.
Metal–insulator–semiconductor structure: A structure in which a thin insulating layer separates a metal from a semiconductor. The intervening dielectric changes charge transfer and electrostatics relative to direct contact.
Schottky–Mott rule: A model that estimates a contact’s barrier height from the metal work function and semiconductor electron affinity. It predicts the ideal barrier before interface states and chemical effects are considered.
Electron affinity: The energy difference between a semiconductor’s vacuum level and conduction-band edge. It helps determine the ideal electron barrier at the contact.
Contact resistance: The resistance to current flow across an electrical contact between materials. It measures a key practical cost of carrier transfer across the junction.
Heterojunction: An interface between two semiconductors with different compositions or band structures. It creates band offsets without requiring one side of the interface to be a metal.
Fermi-level pinning: The restriction of a semiconductor’s interfacial Fermi level to a limited energy range, often by interface states. It explains why measured barrier heights can depart from work-function predictions.
Band bending: The variation of semiconductor energy-band edges with position near an interface or surface. Charge redistribution bends the bands as the metal and semiconductor reach equilibrium.

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