Gunn Diode - OpenStudy

agreementkittensSemiconductor

Nov 2, 2013 (3 years and 9 months ago)

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T
OPIC

O
F

P
RESENTATION


Gunn Diode

G
UNN

D
IODE



Definition



History



Construction







Definition:



S
uch type of semiconductor

device which have only N type doped


(semiconductor) material, is called “Gunn Diode.”



It’s a unique component.



Gunn
D
iode is also known as:


Transferred Electron Device (TED).

Microwave Semiconductor Device.

























Symbols for Circuit Diagram:












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
GaAs




semiconductor, in
1963.



Construction:



Gunn diodes are fabricated from a single piece of n
-
type




semiconductor,



Source Material:




Tri
-
methylgallium

and arsenic
(10% in H2).



M
ost Common Materials :



Gallium Arsenide (GaAs)


and Indium Phosphide (InP).








Three main areas:



Top/Upper Area,


Middle Area,


Bottom Area.



















Middle area (Active layer) has a doping level between


10
14

cm
-
3

to
10
16
cm
-
3

.


Substrate has doping



density



n = 1.3x10 ^18 cm
-
³.






Thickness varies according to the


frequency required.







Metal contacts consist of three layers, namely a



80 nm
layer of
AuGe

sandwiched between two



layers of
10 nm
of
Ni.





Additional
AuGe

is evaporated on the



existing contacts to a depth of
0.7μm.








Use Of Gold.


Its relative stability,


and high conductivity.





Requirements:






The material must be defect free , and it must also



have a very uniform level of doping.







Types of Materials Used For Gunn Diodes




To Get Different Frequencies:





Gallium arsenide for frequencies up



to 200 GHz,



Gallium nitride can reach up to 3 THz.

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UNN

D
IODE

Negative
Resistance


I
n
G
unn
D
iode


GaAs

(
Galliam

Arsenide ) has a property of
negative resistance.


) The negative resistance in Gunn diode is due to

(a) electron transfer to a less mobile energy level

(b) high reverse bias

(c) electron domain formation at the junction


(a)



How electron move into low mobility ?




According to
Einstien

Equation




E=mc2



(b) High reverse bias





(c) Electron domain formation at the


junction


E
FFECT

OF

N
EGATIVE

RESISTANCE

ON

CURRENT

G
UNN

D
IODE





Gunn Effect

G
UNN

DIODE

WHICH

HAS

A

NEGATIVE

DYNAMIC

RESISTANCE
.


G
RAPH

B
ETWEEN

R
ESISTANCE


A
ND

V
OLTAGE


As a result we arrange that
average voltage on the Gunn diode
is as illustrated in
figure.
The
diode is said to be
biased

into the
negative resistance region.







C
HANGE

IN

E
NERGY




R= R
L
+
R
(V)



W
HEN

R

>0



T
HE

ENERGY

OF

ANY

OSCILLATION

TENDS

TO

BE


REDUCED

BY

RESISTIVE

DISSIPATION
.





W
HEN

R

< 0


The
oscillation energy tends to be increased
.



According to law of conservation of energy



The amount of energy at r > 0 = The amount of
energy at r < 0

G
RAPH

B
ETWEEN

R
ESISTANCE

A
ND

C
URRENT

W
ORKING

O
F

G
UNN

D
IODE

C
OAXIAL

CAVITY


In
this case, each diode induced fluctuation
travels up the cavity and reflected from the far
end, returning to the diode after a time




L = length of cavity


c= speed of light



The
oscillator may therefore

oscillate
at any frequency
such
that.



n=
the “number of half
-
waves”

F
OR

A

BETTER

RESULT



n=1


The
system won't oscillate at a lower
frequency because the cavity is too short
to permit it. It can't oscillate at a higher
frequency because the diode is ‘too slow’,
hence we ensure a single
-
valued
oscillation frequency.



Real
Gunn devices have a

response
time which varies
with the applied voltage,
hence we can
electronically
tune

the oscillation frequency
by slightly adjusting the bias
voltage

G
UNN

D
IODE

Difference between Gunn
diode and P
-
N junction

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

Construction


It only consists of N type
semiconductor material


It has N+ n N+ material


No depletion region is
formed




It consists of P & N type
semiconductor material


It has P type,N type and
depletion region between
these materials




Gunn diode

P
-
N junction diode

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

Gunn Doiode

P
-
N junction Diode

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

Symbols of Gunn Diode

P
-
N junction

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

Gunn Doiode

P
-
N junction Diode

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

Gunn Doiode

P
-
N junction Diode

D
IFFERENCE

BETWEEN

G
UNN

DIODE

AND

P
-
N
JUNCTION

I
-
V characteristics

Of Gunn diode

I
-
V characteristics

Of P
-
N junction Diode

G
UNN

D
IODE


Applications


A Gunn diode can be used to amplify signals because of
the apparent "negative resistance". Gunn diodes are
commonly used as a source of high frequency and high
power signals




Sensors and measuring

Instruments




Anti
-
lock brakes



Sensors for monitoring the flow of traffic



Pedestrian safety systems



Distance traveled" recorders



Traffic signal controllers



Automatic traffic gates



AUTOMATIC

DOOR

OPENERS


CAR

SPEED

DETECTORS


SENSORS

TO

AVOID

DERAILMENT

OF

TRAINS



MOTION

DETECTOR


R
ADIO

AMATEUR

USE



G
UN

OSCILLATOR





Thanks!