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A tunnel diode is a high-performance electronic component used in high-speed electronic circuits. It is used as a specific form of semiconductor. Also referred to as the Esaki diode after its inventor, the tunnel diode uses quantum mechanics to produce an extremely fast operating diode.
In 1957, physicist Leo Esaki, working for the company now known as Sony, designed the first palpable tunnel diode after finding that forcing a tunneling effect on electrons created a much faster processing of the signal sent through the diode. He won a jointly earned Nobel Prize for Physics with Brian Josephson in 1973 based on their discovery and design. After the implementation of tunnel diodes for a multitude of electronic devices Sony Corporation manufactured, the use of tunnel diodes expanded quickly to other manufacturers and many created their own tunnel diode designs based on the one created by Esaki.
Tunnel diodes are popular because they are capable of functioning at speeds relative to the region of microwave frequencies. Their design and the materials used to create them allow them to function at such a high rate of speed. This attribute allows the tunnel diode to become a viable part of many different electronic devices, and the tunnel diode has been used by a number of electronics manufacturing companies since its inception.
The reason these diodes are able to function as quickly as they do and create the processing speed they are able to is because of the alignment of the conduction and the valance electron bands within a broken bandgap. This alignment results in the circuit the diode is implemented with being able to process the input signal in a significantly faster fashion. As a result, the tunnel diode can be used in amplifiers and signal processors, as well as in frequency converters and oscillators.
The material the diode is made out of also contributes to the speed at which it is able to function. The diode itself may be fabricated strictly from germanium, a lightweight and ultra-conductive material. This is the material that was primarily used when these types of diodes first became popular.
Later models of the diodes have been made out of other conductive materials. Examples include gallium arsenide as well as silicon-based materials. The use of different materials has either increased or decreased the speed of function for the tunnel diode, according to the use of the diode.