A tunnel diode works by creating an area of negative resistance for electrons to penetrate the potential barrier of a semiconductor junction. The mechanism of a tunnel diode is based on the principle of quantum mechanical tunneling where a particle "tunnels" through a barrier, which it cannot otherwise cross.
A diode is a semiconductor electronic device that allows electricity to pass through in only one direction. A common type of diode is called the p-n junction diode, which consists of two terminals: a p-type substance referred to as the "anode" and an n-type substance called the "cathode." Other types of diodes include the Zener diode, Schottky diode, laser diode, tunnel diode and light emitting diode, or LED.
A tunnel diode, also referred to as the Esaki diode, was named after its discoverer, Leo Esaki. In 1958, Esaki was studying the effects of doping germanium junctions for bipolar transistors. In electronics, doping is the process of adding impurities to semiconductors to regulate electrical resistance. Esaki discovered that by adding large amounts of impurities on a normal junction diode, a negative resistance region forms, which results to a decrease in the depletion region. The reduction in the depletion zone allows particles, such as electrons, to pass through the junction barrier. Tunnel diodes are important components used in a variety of electronic applications. They are specially effective as amplifiers or oscillators.