Editing Gunn diode (section)

{{Short description|Form of diode}}
[[Image:Ganna diode 3A703B.jpg|thumb|A Russian-made Gunn diode]]

A '''Gunn diode''', also known as a '''transferred electron device''' ('''TED'''), is a form of [[diode]], a two-terminal [[semiconductor]] electronic component, with [[negative differential resistance]], used in high-frequency [[electronics]]. It is based on the "Gunn effect" discovered in 1962 by physicist [[J. B. Gunn]]. Its main uses are in [[electronic oscillator]]s to generate [[microwave]]s, in applications such as [[radar speed gun]]s, [[microwave relay]] data link transmitters, and automatic door openers.

Its internal construction is unlike other diodes in that it consists only of [[Doping (semiconductors)|N-doped]] [[semiconductor]] material, whereas most diodes consist of both P and N-doped regions. It, therefore, conducts in both directions and cannot [[Rectifier|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 are heavily N-doped on each terminal, with a thin layer of lightly n-doped material between them. When a voltage is applied to the device, the electrical gradient will be largest across the thin middle layer. If the voltage increases, the layer's current will first increase. Still, eventually, at higher field values, the conductive properties of the middle layer are altered, increasing its resistivity and causing the current to fall. This means a Gunn diode has a region of [[Negative resistance|negative differential resistance]] in its [[current–voltage characteristic]] curve, in which an increase of applied voltage causes a decrease in current. This property allows it to [[amplifier|amplify]], functioning as a radio frequency amplifier, or to become unstable and oscillate when it is [[biasing|biased]] with a DC voltage.