• In multijunction photovoltaic cell
  Multijunction photovoltaic cell
  Multi-junction solar cells or tandem cells are solar cells containing several p-n junctions. Each junction is tuned to a different wavelength of light, reducing one of the largest inherent sources of losses, and thereby increasing efficiency...
  
  s, tunnel junctions form the connections between consecutive solar-cell layers. They function as an ohmic electrical contact
  Ohmic contact
  An ohmic contact is a region on a semiconductor device that has been prepared so that the current-voltage curve of the device is linear and symmetric. If the I-V characteristic is non-linear and asymmetric, the contact is not ohmic, but is a blocking or Schottky contact...
  
  in the middle of a semiconductor
  Semiconductor
  A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
  
   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 Josephson junctions, two superconducting electrodes are separated by a non-superconducting barrier. Cooper pair
  Cooper pair
  In condensed matter physics, a Cooper pair or BCS pair is two electrons that are bound together at low temperatures in a certain manner first described in 1956 by American physicist Leon Cooper...
  
  s of electrons carry the current through the barrier by tunneling. This setup can form the basis for extremely sensitive magnetometers, as well as many other devices.

• In tunnel diode
  Tunnel diode
  A tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave frequency region, by using quantum mechanical effects....
  
  s, 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
  Quantum tunnelling
  Quantum tunnelling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an essential role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the sun, and has important...
  
  
• Ferroelectricity
  Ferroelectricity
  Ferroelectricity is a property of certain materials which possess a spontaneous electric polarization that can be reversed by the application of an external electric field. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was...
  
   (Ferroelectric tunnel junction)
• Josephson effect
  Josephson effect
  The Josephson effect is the phenomenon of supercurrent across two superconductors coupled by a weak link...
  
   (superconduction)
• Coulomb blockade
  Coulomb blockade
  In physics, a Coulomb blockade , named after Charles-Augustin de Coulomb's electrical force, is the increased resistance at small bias voltages of an electronic device comprising at least one low-capacitance tunnel junction. Because of the CB, the resistances of devices are not constant at low bias...
  
  
• Tunnel diode
  Tunnel diode
  A tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave frequency region, by using quantum mechanical effects....