Tunnel junction

In electronics, a tunnel junction is a barrier between two materials that electrons pass through by the process of quantum tunneling. Tunnel junctions serve a variety of different purposes.

• In multijunction photovoltaic cells, tunnel junctions form the connections between consecutive solar-cell layers. They function as an ohmic electrical contact in the middle of a semiconductor device.

• In magnetic tunnel junctions, electrons tunnel through a thin insulating barrier from one magnetic material to another. This can serve as a basis for a magnetic detector.

• In superconducting tunnel junctions, two superconducting electrodes are separated by a non-superconducting barrier. Cooper pairs carry the supercurrent through the barrier by quantum tunneling, a phenomenon known as the Josephson effect. This setup can form the basis for extremely sensitive magnetometers, known as SQUIDs, as well as many other devices.

• In tunnel diodes, a diode is made to allow tunneling of electrons through it, for certain voltages. This, it turns out, allows them to be used for generating high-frequency signals.

See also

• Quantum tunnelling
• Ferroelectricity (Ferroelectric tunnel junction)
• Superconducting tunnel junction
• Josephson effect
• Coulomb blockade
• Tunnel diode