Ohmic contact

An electrical junction that obeys Ohm's law

Ohmic contact

An ohmic contact is a region on a semiconductor device that has been engineered to have a very low resistance and allows current to pass through it easily, following Ohm's law. This type of contact is crucial in semiconductor devices as it ensures efficient current injection or extraction without significant voltage drop.

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Schematic representation of an ohmic contact

Characteristics

Ohmic contacts are characterized by their linear current-voltage (I-V) relationship, meaning that the current through the contact is directly proportional to the voltage across it. This linearity is essential for the predictable performance of electronic devices.

Formation

The formation of an ohmic contact involves creating a metal-semiconductor junction that does not rectify current. This can be achieved by:

• Doping: Increasing the doping concentration at the contact region to reduce the barrier height.
• Metal selection: Choosing metals with appropriate work functions to align with the semiconductor's energy bands.
• Annealing: Applying heat treatment to improve the contact interface by reducing defects and forming intermetallic compounds.

Applications

Ohmic contacts are used in various semiconductor devices, including:

• Diodes
• Transistors
• Integrated circuits

These contacts are essential for ensuring that the devices operate efficiently and reliably.

Challenges

Creating a perfect ohmic contact can be challenging due to:

• Material compatibility: Ensuring that the metal and semiconductor materials are compatible and do not form unwanted compounds.
• Surface preparation: Achieving a clean and smooth surface to minimize contact resistance.
• Thermal stability: Ensuring that the contact remains stable under operating conditions.

Related pages

• Schottky contact
• Semiconductor device
• Ohm's law