397988642-Photodiode-Investigatory-project-docx-docx.pdf

KENDRIYA VIDYALAYA
INA COLONY
NEW DELHI – 23
2016-17

FROM :- DEEPANKAR
BOSE
CLASS :- 12
SECTION :- A
ROLL NO :- 9197670
ACKNOWLEDGEMENT

In the accomplishment of this project
successfully, I would like to thank my
principal Mr. V.K. Tyagi
and physics teacher Dr. Naveen Kumar,
whose valuable guidance has been the ones
that helped me patch this project and make it
full proof success his suggestions and his
instructions has served as the major
contributor towards the completion of the
project.
Last but not the least I would like to thank
my classmates who have helped me a lot.
CERTIFICATE

This is to certify that
DEEPANKAR BOSE, a student
of class XII-A has successfully
completed the investigatory
project under my guidance
during the year 2016 – 17 and
his work is original.
(Signature)
Physics Teacher

INDEX
1) Introduction
2) Photodiode
3) Types of Photodiode
4) Material Required
5) Working
6) Modes of Operation
7) V-I Characteristics
8) Applications
9) Conclusion
INTRODUCTION :-

A photodiode is a PN-
junction diode that
consumes light energy
to produce electric
current. Sometimes it is
also called as photo-
detector, a light
detector, and photo-
sensor. These diodes
are particularly designed
to work in reverse bias
condition, it means that
the P-side of the
photodiode is
associated with the

negative terminal of the
battery and n-side is
connected to the
positive terminal of the
battery.
 A photodiode is one type of light detector, used to convert the
light into current or voltage based on the mode of operation of
the device.
 It comprises of optical filters, built-in lenses and also surface
areas.
 These diodes have a slow response time when the surface area
of the photodiode increases.
 Photodiodes are alike to regular semiconductor diodes.

 They may be either visible to let light reach the delicate part of
the device.
 Several diodes intended for use exactly as a photodiode will also
use a PIN junction somewhat than the usual PN junction.
See the following schematic diagram for the anode and
cathode side.

 Under forward bias condition, conventional current will
flow from the anode to the cathode, following the arrow
in the diode symbol.
 Photocurrent flows in the reverse direction.

TYPES OF PHOTODIODES
 The types of the photodiodes can be
classified based on its construction
and functions as follows :-
- PN Photodiode
- Schottky Photo Diode
- PIN Photodiode
- Avalanche Photodiode

The main features of photodiodes are as
following :-
 These diodes are widely
used in different
applications
 Where the detection of the
presence of light, colour,
position, intensity is
required
 The linearity of the diode
is good with respect to
incident light
 Noise is low
 The response is wide
spectral

 Rugged mechanically
 Light weight and compact
 Long life
MATERIALS REQUIRED TO MAKE
A PHOTODIODE :
 For Lead (II) sulfide material: The
electromagnetic spectrum wavelength
range will be <1000-3500) nm
 For Mercury, cadmium Telluride
material: The electromagnetic
spectrum wavelength range will be
(400-14000) nm

 Because of their better band gap, Si-
based photodiodes produce lower
noise than Ge-based photodiodes.
WORKING OF
PHOTODIODE
 When a photon of ample
energy strikes the diode.
 It makes a couple of an
electron-hole.
 This mechanism is also
called as the inner
photoelectric effect.

 If the absorption arises
in the depletion region
junction.
 Then the carriers are
removed from the junction
by the inbuilt electric
field of the depletion
region.
 The holes in the region
move toward the anode, and
electrons move toward the
cathode, and a photocurrent
will be generated.
 The entire current
through the diode is the

sum of the absence of light
and the photocurrent.
 So the absent current
must be reduced to maximize
the sensitivity of the
device.
MODES OF OPERATION

•Photovoltaic mode
•Photoconductive mode
•Avalanche diode mode
Photovoltaic Mode:

This mode is also known as
zero bias mode.
-In which a voltage is produced
by the lightened photodiode.
-It gives a very small dynamic
range & non-linear necessity of
the voltage formed.
Photoconductive Mode

The photodiode used in this
photoconductive mode is more
usually reverse biased.
-The reverse voltage
application will increase the
depletion layer’s width.
-Which in turn decreases the
response time & the junction
capacitance.
-This mode is too fast and
displays electronic noise.

Avalanche Diode Mode
-Avalanche diodes
operate in a high
reverse bias
condition.
-Which permits
multiplication of
an avalanche
breakdown to each
photo-produced

electron-hole
pair.
-This outcome in
an internal gain
in the photodiode,
which slowly
increases the
device response.
V-I Characteristics of
Photodiode

A photodiode continually
operates in a reverse bias mode.
-The photocurrent is nearly
independent of reverse bias
voltage which is applied.
-For zero luminance, the
photocurrent is almost zero
excluding for small dark
current.
The characteristics of the photodiode are
shown clearly in the following figure

Applications of
Photodiode
The applications of photodiodes involve
in similar applications of photodetectors
like charge-coupled devices,

photoconductors, and photomultiplier
tubes.
These diodes are used in consumer
electronics devices like smoke detectors,
compact disc players, televisions and
remote controls in VCRs.
It uses in consumer devices like clock
radios, camera light meters, and street
lights.
Photodiodes are also widely used
in numerous medical applications like
instruments to analyse samples, detectors
for computed tomography and also used
in blood gas monitors.
These diodes are much faster & more
complex than normal PN junction diodes.
It is frequently used for lighting
regulation and in optical communications.
CONCLUSION

A photodiode is a kind of
light detector, which
involves the conversion
of light into voltage or
current, based on the
mode of operation of the
device. A photodiode is a
semi-conductor device,
with a p-n junction and
an intrinsic layer
between p and n layers.

Bibliography
o NCERT
textbooks
o Physics
Practical books
o Wikipedia
o I-CBSE.com

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