page_title: Gunn diode
section_title: History
hierarchical_section_title: Gunn diode / History
caption_attribution_description: English: A Gunn diode microwave oscillator M31102-1. It consists of a Gunn diode mounted in a cavity resonator, biased with a DC voltage supplied by the wires in the background. The negative resistance of the diode cancels the positive resistance of the cavity, exciting microwave oscillations at the resonant frequency of the cavity. The microwaves radiate out the aperture into a waveguide which is bolted to the front (not shown). The frequency of the waves produced can be changed by adjusting the thumbscrew, which changes the size and thus the resonant frequency of the cavity. Latviešu: Ganna ģenerators M31102-1. Redzama viļņvada izeja, aizsegta ar radiocaurspīdīgas keramikas plāksnīti violetā krāsā.
context_page_description: A Gunn diode, also known as a transferred electron device, is a form of diode, a two-terminal semiconductor electronic component, with negative resistance, used in high-frequency electronics. It is based on the "Gunn effect" discovered in 1962 by physicist J. B. Gunn. Its largest use is in electronic oscillators to generate microwaves, in applications such as radar speed guns, microwave relay data link transmitters, and automatic door openers.
  Its internal construction is unlike other diodes in that it consists only of N-doped semiconductor material, whereas most diodes consist of both P and N-doped regions. It therefore does not conduct in only one direction and cannot rectify alternating current like other diodes, which is why some sources do not use the term diode but prefer TED. In the Gunn diode, three regions exist: two of those are heavily N-doped on each terminal, with a thin layer of lightly n-doped material between. When a voltage is applied to the device, the electrical gradient will be largest across the thin middle layer.
context_section_description: The Gunn diode is based on the Gunn effect, and both are named for the physicist J. B. Gunn who, at IBM in 1962, discovered the effect because he refused to accept inconsistent experimental results in gallium arsenide as "noise", and tracked down the cause.  Alan Chynoweth, of Bell Telephone Laboratories, showed in June 1965 that only a transferred-electron mechanism could explain the experimental results.  It was realized that the oscillations he detected were explained by the Ridley–Watkins–Hilsum theory, named for British physicists Brian Ridley, Tom Watkins and Cyril Hilsum who in scientific papers in 1961 showed that bulk semiconductors could display negative resistance, meaning that increasing the applied voltage causes the current to decrease.
  The Gunn effect, and its relation to the Watkins–Ridley–Hilsum effect entered electronics literature in the early 1970s, e.g. in books on transferred electron devices and, more recently on nonlinear wave methods for charge transport.
caption: Russian Gunn diode oscillator. The diode is mounted inside the cavity (metal box), which functions as a resonator to determine the frequency.  The negative resistance of the diode excites microwave oscillations in the cavity which radiate out the hole into a waveguide (not shown).   The frequency can be adjusted by changing the size of the cavity using the thumbscrew.
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