tunneljunction

A tunnel junction is a thin insulating layer sandwiched between two conductive materials. This structure allows electrons to "tunnel" through the insulating barrier via quantum mechanical tunneling, even though they classically lack the energy to overcome it. The probability of tunneling is highly dependent on the thickness and material properties of the insulating layer.

Tunnel junctions are fundamental components in various electronic devices. One prominent application is in magnetic tunnel junctions (MTJs), which are crucial for magnetoresistive random-access memory (MRAM) and magnetic sensors. In MTJs, the insulating barrier is typically a few nanometers thick, and the conductivity of the junction changes significantly depending on the relative magnetic orientation of the two conductive layers. This change in resistance, known as the tunnel magnetoresistance (TMR) effect, is exploited to store and read data in MRAM.

Another important type is the superconducting tunnel junction. When two superconductors are separated by a thin insulating layer, Cooper pairs of electrons can tunnel across the barrier. These junctions are used in highly sensitive detectors for electromagnetic radiation, such as superconducting nanowire single-photon detectors (SNSPDs) and in quantum computing applications. The unique quantum mechanical properties of tunnel junctions make them indispensable for a wide range of advanced technologies.