EsakiDiode

The Esaki diode, also known as the tunnel diode, is a semiconductor device that exhibits negative differential resistance. It was invented by Leo Esaki in 1957. This unique characteristic means that as the voltage across the diode increases, the current flowing through it actually decreases over a certain range. This behavior is due to quantum mechanical tunneling, where electrons can pass through an energy barrier even if they do not have enough energy to overcome it classically.

Esaki diodes are heavily doped, meaning they have a very high concentration of impurity atoms. This heavy doping creates a very narrow depletion region. When a small forward voltage is applied, electrons can tunnel across this narrow depletion region from the valence band of the p-type material to the conduction band of the n-type material. As the forward voltage increases further, the energy bands align in such a way that tunneling becomes less probable, leading to a decrease in current. Eventually, at higher forward voltages, the diode behaves like a conventional diode.

The negative differential resistance region makes Esaki diodes useful in high-frequency applications, such as oscillators and amplifiers. They can also be used in switching circuits due to their fast switching speeds. However, their very low power handling capabilities and sensitivity to temperature limit their widespread use compared to other semiconductor devices. Esaki diodes are typically made from gallium arsenide or germanium.