Final Gunn - Copy2

8/13/2019 Final Gunn - Copy2

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History

Gunn diode was invented by a Physicist,John

Battiscombe Gunn, in 1963, in IBM.

Transferred Electron Effect was first

published by:Ridley and Watkins in 1961.

Further work by Hilsum in 1962

Finally J.B. Gunn observed it using

GaAssemiconductor, in 1963.



Explanation for Gunn Effect:

Ridley – Watkins – Hilsum (RWH)

Theory

Two concepts related with RWH

Theory.

Differential negative resistanceTwo valley model



The current waveform was produced by

applying a voltage pulse of 16V and

10ns duration to an n-type GaAs of 2.5x 10-3 cm length. The oscillation

frequency was 4.5Ghz



Direct Band Gap Semiconductors







1. The energy difference between two valleys

must be several times

larger than the thermal energy (KT~0.0259eV)

2. The energy difference between the valleys

must be smaller than the bandgap energy (Eg)

3. Electron in lower valley must have a highermobility and smaller effective mass than that

of in upper valley

Two-Valley Model

Theory





What is Gun Diode ?

A Gunn diode is also known as a transferred

electron device (TED). It is a form of diode

used in high-frequency electronics. 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 forfrequencies up to 200GHz.







Gunn Diode ConstructionThe 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 goldconnection deposited onto the top surface.



The centre area of the device is the active

region.

This region is also less heavily doped and this

means that virtually all the voltage placedacross the device appears across this region.

In view of the fact that the device consists only

of n type material there is no p-n junction and in

fact it is not a true diode, and it operates ontotally different principles.





Data for two valleys in GaAs







ADVANTAGES

It has much lower noise than IMPATT diodes

Higher peak-to-valley ratio in its – ve resistance

characteristics.

High fundamental frequency operation.

Increased efficiency.

GUNN DIODE









gunn diode oscillator



Gunn Oscillator

In a Gunn Oscillator, the Gunn Diode is

placed in a resonant cavity. In this case

the oscillationfrequency is determined by cavity

dimension than by the diode itself.

Although Gun Oscillator

can be amplitude-modulated with thebias voltage, we have used separate

PIN modulator through

PIN diode for square wave modulation.





Gunn diode oscillators are used to

generate microwave power for airbornecollision avoidance radar, anti-lock

brakes, sensors for monitoring the flow

of traffic, car radar

detectors,pedestrian safety systems,"distance traveled" recorders, motion

detectors,





Russian 3A703A Military GaAs Gunn diode 12.5GHzMicrowave diodes are designed for operation infrequency multipliers of dm, cm and mm-wave

bands.

AA or 3A means arsenide-gallium diodes

Metal-ceramic body, Goldplated New, OldstockFrequency range 8.24...12.5GHz

Operating current, max. 270mA

Inductance 1.7nH

Diode resistance 3...20 Ohm

Nominal voltage, DC 8.5...9V

Output Power 25mW



USSR-/ ex8625E / DGB715AAGunn Oscillator DiodeGaAs

1GHz QTY=11.5

UkraineItem sold in:price $22.95

GunnGaAsA,736A,AA736A3

mW35GHz18Oscillator diode

10Oty

Item sold in:

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http://www.ebay.com/itm/3A736A-AA736A-GaAs-Gunn-Oscillator-diode-18GHz-35mW-Oty-10-/261284859893















































GaAsB Military703A3GHz12.5Gunn diode

10Oty:Item sold in:price

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$99.0

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Parameters at T = +25 C

Name

Frequen

cy

range,

GHz

Output

power,

mW

Operatin

g

current,

A

Operati

ng

voltage

, V

Efficien

cy, %

Diode

resistan

ce, Ohm

Case

capacita

nce, pF

Inducta

nce, nH

Temperat

ure

range, C

1 2 3 4 5 6 7 8 9 10

AA7715E 10…

11.5100…240 0.5…1.2 9.5 >1.5 0.6…2.5 0.5 0.5 -60…+70

Documents

Final Gunn - Copy2