Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages Introduction To Semiconductors Metal–Semiconductor Junction – Ohmic Contact
Introduction To Semiconductors AimsBefore you startIntroductionIntroduction to Energy BandsThe Fermi–Dirac DistributionCharge Carriers in SemiconductorsIntrinsic and Extrinsic SemiconductorsDirect and Indirect Band Gap SemiconductorsCompound SemiconductorsBehaviour of the Fermi EnergyMetal–Semiconductor Junction – Rectifying ContactMetal–Semiconductor Junction – Ohmic ContactThe p–n JunctionBipolar TransistorMetal Oxide Semiconductor Field Effect Transistor (MOSFET)SummaryQuestionsGoing further
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Metal–Semiconductor Junction – Ohmic Contact

When a metal and an n-type semiconductor are joined and φm < φs, electrons will flow from the Fermi energy level in the metal into the semiconductor conduction band to lower their energy. This will cause the Fermi energy of the semiconductor to move up into equilibrium with that of the metal. It will also deform the semiconductor bands, so that they curve upwards away from the metal. This situation is depicted in the animation below. Use the tabs to navigate through the animation.

This type of contact yields a linear relationship between the voltage applied and the current that flows across the junction. It is therefore called an Ohmic contact, because it obeys Ohm's law. This type of contact is also described as metallization, and is used to supply electric current into semiconductor devices.

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