8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 1/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 2/31
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.
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 3/31
Explanation for Gunn Effect:
Ridley – Watkins – Hilsum (RWH)
Theory
Two concepts related with RWH
Theory.
Differential negative resistanceTwo valley model
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 4/31
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
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 5/31
Direct Band Gap Semiconductors
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 6/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 7/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 8/31
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
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 9/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 10/31
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.
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 11/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 12/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 13/31
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.
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 14/31
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.
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 15/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 16/31
Data for two valleys in GaAs
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 17/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 18/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 19/31
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
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 20/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 21/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 22/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 23/31
gunn diode oscillator
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 24/31
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.
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 25/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 26/31
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,
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 27/31
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 28/31
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
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 29/31
USSR-/ ex8625E / DGB715AAGunn Oscillator DiodeGaAs
1GHz QTY=11.5
UkraineItem sold in:price $22.95
GunnGaAsA,736A,AA736A3
mW35GHz18Oscillator diode
10Oty
Item sold in:
price $99.0
Romania
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 30/31
GaAsB Military703A3GHz12.5Gunn diode
10Oty:Item sold in:price
Romania
$99.0
8/13/2019 Final Gunn - Copy2
http://slidepdf.com/reader/full/final-gunn-copy2 31/31
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
Top Related