In a tunnel junction, electrons can traverse the thin insulating barrier even when they do not possess sufficient energy to overcome it classically. This process, known as quantum tunneling, occurs due to the probabilistic nature of quantum mechanics, where there is a finite probability for an electron to pass through the barrier.
The probability of tunneling is exponentially related to the thickness and height of the barrier. Therefore, even a minor reduction in the barrier's thickness can substantially increase the tunneling current. This sensitivity makes tunnel junctions highly useful in nanoscale applications.
