tunnel diode
The tunnel diode has a characteristic curve in the reverse direction which represents a negative resistance in a certain range. It is also called Esaki diode after its inventor.
The name tunnel diode is related to the tunnel that forms in the reverse direction due to the high doping. The small germanium layer of N material alloyed with indium contributes to this. There is no comparable reverse function as with other diodes.
The I-V-characteristic shows a reduction of the current flow in the range with increasing voltage, which corresponds to a negative differential resistance value. Above and below this range, the tunnel diode shows positive resistance values. In forward direction, the tunnel diode has the same characteristics as normal diodes.
Tunnel diodes are used, among other things, in oscillators for the generation of high frequencies.