Download Schottky diode I-V Characteristics

Faculty of Degree Engineering - 083
Department of Electronic& communication
Engineering - 11
Subject: EDC (2131006)
Topic: Schottky Diode
Prepared By:
Hardik Thumar (140830111005)
Kundan Vaghela (140830111006)
Guided By: Prof. N.Y.Chavda
SCHOTTKY BARRIER DIODE
•The Schottky diode (named after German
physicist Walter H. Schottky; also known as hot
carrier diode) is a semiconductor diode with a low
forward voltage drop and a very fast switching
action.
•When current flows through a diode there is a
small voltage drop across the diode terminals. A
normal silicon diode has a voltage drop between
• A metal–semiconductor
junction is formed
CONSTRUCTION
between a metal and a semiconductor, creating a
Schottky barrier (instead of a semiconductor–
semiconductor junction as in conventional
diodes).
• Typical metals used are molybdenum, platinum,
chromium or tungsten; and the semiconductor
would typically be N-type silicon.
• The metal side acts as the anode and N-type
semiconductor acts as the cathode of the diode.
This Schottky barrier results in both very fast
switching and low forward voltage drop.
Reverse recovery time
• The most important difference between the
p-n and Schottky diode is reverse recovery
time, when the diode switches from
conducting to non-conducting state. Where
in a p-n diode the reverse recovery time can
be in the order of hundreds of nanoseconds
and less than 100 ns for fast diodes,
Schottky diodes do not have a recovery
time, as there is nothing to recover from
(i.e. no charge carrier depletion region at the
junction).
•
CONSTRUCTION
AND
It is often said that the Schottky diode is a
"majorityAPPLICATIONS
carrier" semiconductor device.
This means that if the semiconductor body
is doped n-type, only the n-type carriers
(mobile electrons) play a significant role in
normal operation of the device. The
majority carriers are quickly injected into
the conduction band of the metal contact on
the other side of the diode to become free
moving electrons. Therefore no slow,
random recombination of n- and p- type
carriers is involved, so that this diode can
• This is another reason why Schottky diodes
are useful in switch-mode power converters;
the high speed of the diode means that the
circuit can operate at frequencies in the
range 200 kHz to 2 MHz, allowing the use
of small inductors and capacitors with
greater efficiency than would be possible
with other diode types. Small-area Schottky
diodes are the heart of RF detectors and
mixers, which often operate up to 50 GHz.
Limitations
• The most evident limitations of Schottky
diodes are the relatively low reverse voltage
ratings for silicon-metal Schottky diodes,
typically 50 V and below, and a relatively
high reverse leakage current. Some highervoltage designs are available; 200V is
considered a high reverse voltage.
*Other Two-Terminal Devices
*Schottky Barrier Diodes
Two-Terminal Devices Having A
Single p-n Junction
Schottky
Tunnel
Varactor
Photodiode
Solar Cell
Other Two-Terminal Devices
Of A Different Construction
Photoconductive Cell
LCD (Liquid-Crystal Display)
Thermistor
Schottky-Barrier Diode
*Surface-Barrier/Hot-Carrier Diode
Schottky Diode
Areas of Application
Very high frequency range
Lower noise figure
Low-voltage or high-current power supplies
AC-to-DC converters
Radar systems
Schottky TTL logic
Schottky/ hot-carrier diode
Gold leaf metal contact
Anode (+)
Metal
Silicon dioxide screen
Metal semiconductor junction
Metal contact
Cathode (-)
Comparison of characteristics of hotcarrier and p-n junction diodes
ID
Hot
carrier
diode
p-n
junction
diode
VD
p-n
junction
diode
Hot
carrier
diode
Fig. 20.5 Motorola Schottky barrier devices.
(Courtesy Motorola Semiconductor Products, Incorporated
IO Average rectified forward current (amperes)
VRRM
(Volts)
Case
Anode
Cathode
59-04
Plastic
MBR4040
800
430-2
(DO-21)
Metal
MBR4030
IN5833
MBR2530
IN5830
MBR1530
IN5827
IN5824
IN5821
MBR4035
MBR2535
MBR1535
MBR335M
MBR335P
MBR135P
MBR4020PF MBR4030PF MBR4035PF
IN5834
800
MBR4020
MBR2534
800
IN5832
IN5831
800
MBR2520
MBR1540
500
IN5829
IN5828
500
MBR1520
IN5825
500
IN5826
MBR340M
500
IN5823
MBR340P
200
MBR330M
IN5822
MBR320M
MBR140P
250
MBR330P
MBR130P
IN5819
Max VF @ IFM = IO
MBR320P
MBR120P
IN5818
50
IN5820
IN5817
TJ Max
257
(DO-5)
Metal
100
40
TC @ Rated IO (ºC)
257
(DO-4)
Metal
60
Metal
5.0
35
IFSM (Amps)
267
Plastic
MBR030
30
MBR020
20
51-02
(DO-7)
Glass
800
85
80
85
80
75
70
50
125ºC
I-V characteristics


I  I s  e

qVA
kT
 1

Where Is = Saturation current q = charge , VA is applied voltage,
k = boltzman constant, and T= Temperature.
The reverse leakage current for a Schottky diode is generally
much larger than that for a p+n diode.