30-08-2013, 02:16 PM
Gunn diode
[attachment=57609]
Introduction
A Gunn diode is also known as a transferred electron device (TED). It is a form of diode used in high-frequency electronics. It is somewhat unusual that it consists only of n-doped semiconductor material, whereas most diodes consist of both P and N-doped regions. In practice, a Gunn diode has a region of negative differential resistance.
Gallium Arsenide Gunn Diodes are made for frequencies up to 200GHz whereas Gallium Nitride can reach upto 3THz.
Principle
It consists of a slice with a buffer layer between the active layer and the substrate, mounted in any of a number of packages,depending on the manufacturer,the frequency and the power level.
They are grown epitaxially out of GaAs with silicon,or selenium.The substrate used here as an ohmic contact, is highly doped for good conductivity,while the thin active layer is less heavily doped.
Diodes have been made with active layers varying in thickness from 40 to about 1 mm at the highest.The actual structure is normally square, and so far GaAs diodes predominate commercially.
Gunn Diode Construction
The top and bottom areas of the device are heavily doped to give N+ material. The device is mounted on a conducting base to which a wire connection is made.
It also acts as a heat-sink for the heat which is generated. The connection to the other terminal of the diode is made via a gold connection deposited onto the top surface.
Operation of Gunn Diode
When a voltage is placed across the device, most of the voltage appears across the inner active region. As this is particularly thin this means that the voltage gradient that exists in this region is exceedingly high.
It is found that when the voltage across the active region reaches a certain point a current is initiated and travels across the active region.
APLICATIONS
Traffic signal actuators.
Door opening sensors.
Low frequency , high frequency operation and medium RF power
[attachment=57609]
Introduction
A Gunn diode is also known as a transferred electron device (TED). It is a form of diode used in high-frequency electronics. It is somewhat unusual that it consists only of n-doped semiconductor material, whereas most diodes consist of both P and N-doped regions. In practice, a Gunn diode has a region of negative differential resistance.
Gallium Arsenide Gunn Diodes are made for frequencies up to 200GHz whereas Gallium Nitride can reach upto 3THz.
Principle
It consists of a slice with a buffer layer between the active layer and the substrate, mounted in any of a number of packages,depending on the manufacturer,the frequency and the power level.
They are grown epitaxially out of GaAs with silicon,or selenium.The substrate used here as an ohmic contact, is highly doped for good conductivity,while the thin active layer is less heavily doped.
Diodes have been made with active layers varying in thickness from 40 to about 1 mm at the highest.The actual structure is normally square, and so far GaAs diodes predominate commercially.
Gunn Diode Construction
The top and bottom areas of the device are heavily doped to give N+ material. The device is mounted on a conducting base to which a wire connection is made.
It also acts as a heat-sink for the heat which is generated. The connection to the other terminal of the diode is made via a gold connection deposited onto the top surface.
Operation of Gunn Diode
When a voltage is placed across the device, most of the voltage appears across the inner active region. As this is particularly thin this means that the voltage gradient that exists in this region is exceedingly high.
It is found that when the voltage across the active region reaches a certain point a current is initiated and travels across the active region.
APLICATIONS
Traffic signal actuators.
Door opening sensors.
Low frequency , high frequency operation and medium RF power