This is a simple diode that exhibits non-linear impedance. These diodes are mostly used at microwave detection and mixing.
A semi-conductor pellet is mounted on a metal base. A spring-loaded wire is connected with a sharp point to this silicon pellet. This can be easily mounted into coaxial or waveguide lines. The below figure gives a clear picture of this.
With the contact between semiconductor and the metal, a depletion region is formed. The metal region has a smaller depletion width, comparatively. When contact is made, electron flow occurs from semi-conductor to the metal. This depletion builds up a positive space charge in the semiconductor and electric field opposes further flow, which leads to the creation of a barrier at the interface.
During forward bias, the barrier height is reduced and electrons get injected into the metal whereas in reverse bias, the barrier height gets increased and the electron injection almost stops.
These are the following advantages
These are the following applications