Gunndiodit

Gunndiodit, also known as Gunn diodes or transferred-electron devices (TEDs), are a type of semiconductor diode that exhibits a unique property called the Gunn effect. This effect allows them to generate microwave frequencies, making them useful in various electronic applications.

The Gunn effect occurs in certain semiconductor materials, typically n-type gallium arsenide (GaAs) or indium phosphide (InP), when a sufficiently high electric field is applied. At low electric fields, electrons in these materials move with a velocity proportional to the field. However, as the field increases, electrons gain enough energy to transfer to a higher energy valley in the material's band structure. This higher energy valley has a lower mobility, meaning the electrons move more slowly. The result is a region of negative differential resistance, where an increase in voltage leads to a decrease in current.

This negative differential resistance characteristic is crucial for the operation of Gunn diodes. When placed in a resonant circuit, the diode can oscillate, producing microwave signals. The frequency of oscillation is primarily determined by the transit time of electrons across the active region of the diode, which is related to the physical dimensions of the device.

Gunn diodes are commonly used as oscillators in microwave systems, including radar transmitters, electronic countermeasures, and local oscillators in communication receivers. They are also employed in some types of intrusion alarms and speed detection devices. Their advantages include simplicity, small size, and relatively high efficiency at microwave frequencies. However, they generally have lower power output compared to other microwave sources like klystrons or magnetrons.