Document that explains the chosen concept to the animator

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Document that explains the chosen concept to the animator

1

Extrinsic Semiconductors

An extrinsic semiconductor is one in which impurities contribute a
significant fraction of the conduction band electrons and/or
valence band holes.

Authors

Anura.B.Kenkre


Course Name: Semiconducting Properties of materials.


2

Learning Objectives

After interacting with this Learning Object, the learner will be able to:


Define an extrinsic semiconductor.


Predict the effect of doping on the conductivity of the extrinsic
semiconductors.


Interpret the difference between n type and p type
semiconductors.



3

Definitions of the components/Keywords:

5

3

2

4

1


An
Extrinsic semiconductor

is one in which impurities contribute a
significant fraction of the conduction band electrons and/or valence
band holes.


when impurity atoms are added to a semiconductor crystal, to
increase either the number of free electrons or the number of holes,
the process is referred to as
Doping.


Impurities that contribute to the carrier density of a semiconductor are
called
donors

if they supply additional electrons to the conduction
band, and
acceptors

if they supply additional holes to (i.e. capture
electrons from)the valence band.


4

5

IMPORTANT NOTE TO THE ANIMATOR:



All the instructions/labels or anything
WRITTEN

in blue
are CONTENT NOT TO BE DISPLAYED!



All the instructions
WRITTEN

in black are CONTENT TO
BE DISPLAYED!



This is not applicable for images as there can be
overlapping of these colours there. This should be
followed for all the instructions,labels,etc…


Kindly keep a note of this while displaying text in the
animation.

Master layout or diagram



Make a schematic diagram of the concept


Explain
to
the animator about the beginning and ending
of the process.


Draw image big enough for explaining.


In above image, identify and label different components
of the process/phenomenon. (
These are like characters
in a film
)



Illustrate the basic flow of action by using arrows. Use
BOLD lines
in the diagram, (minimum
2
pts.)



In the slide after that, provide the definitions of
ALL

the
labels used in the diagram

5

3

2

4

1

INSTRUCTIONS SLIDE

6

Master layout or diagram



You may have multiple master
layouts.


In this case, number the master
layout. ( e.g. Master layout
1
)




Each Master layout should be
followed by the stepwise description
of the animation stages related to it.

5

3

2

4

1

INSTRUCTIONS SLIDE

7

Master Layout 1

5

3

2

4

1

8

Valence Band

Conduction Band

Hole

Hole

Hole

Electrons

This is called the energy band diagram

This is called the
conduction band

This is called the
valence band

This is a hole

This is an
electron

-

-

-

Master Layout 2

5

3

2

4

1

9

+

-


Si

Doping

0

max

This is a power
supply.

Display ‘’12 V’ here.

This is a bulb

These are
wires

This is the
sample(silicon)
and Si is the
symbol of silicon

This is the
slider bar
for doping

These are the boundary
limits of the slider bar

Master Layout 3

5

3

2

4

1

10

σ

(mho/m)

N
D
(/m
3

)

This is a graph

This is the
y axis and
σ

(mho/m)
is the
heading of
the axis



This is the
x axis and
N
D
(/m
3

)

is the
heading of
the axis



These are the
points on the
graph

Animation design


Please see the design template
provided in the next slide.


This is a sample template, and you
are free to change as per your design
requirements.


Try and recreate the
sections/subsections as shown in the
template.



1

5

2

4

3

11

Credits

12

Play/pause

Restart

Want to know more…

(Further Reading)


Definitions

Test your understanding

(questionnaire)


Lets Learn!

Lets Sum up (summary
)


σ

(mho/m)

N
D
(/m
3

)

Valence Band

Conduction Band

Atomic Structure

(Display as a mouse
over)

+

-


Si

Doping

0

max

Experimental set up

Energy Band Diagram

Graph of
σ

versus N

These heading
will change
according to the
step.follow the
step wise
decription for
the correct
heading to be
placed

Pentavalent

Impurity

Trivalent
Impurity

Slide 3

Slide
4

Slide
34
-

39

Slide 42

Slide
40

Explain the process

1

5

3

2

4


In this step, use an example to explain the concept. It
can be an analogy, a scenario, or an action which
explains this concept/process/topic



Try to use examples from day
-
to
-
day life to make it
more clear



You have to describe what steps the animator should
take to make your concept come alive as a series of
moving images.



Keep the examples simple to understand, and also to
illustrate/animate.



13

Stepwise description of process


The goal of the
document

is to provide instructions to an animator
who is not a expert.



You have to describe what steps the animator should take to make
your concept come alive as a moving visualization.



Use one slide per step. This will ensure clarity of the explanation.



Add a image of the step in the box, and the details in the table
below the box.



You can use any images for reference, but mention about it's
copyright status



The animator will have to re
-
draw / re
-
create the drawings



Add more slides as per the requirement of the animation



1

5

3

2

4

14



a) By increasing number of free electrons



b)

By increasing number of holes



c)

Both a and b



c)

Either a or b but not both

15

We know that the intrinsic semiconductor has little current conduction
capability at room temperature. In order to be useful in electronic devices, how
would you alter the properties of a pure semiconductor so as to significantly
increase its conductivity?

Step
1
:

1

5

3

2

4

Instruction for the
animator:

Description of the action/ interactivity

Feedback

Refer to slide
15

Feedback for option a:

That’s correct!

Such a semiconductor is called n type semiconductor.

There's yet another way to increase its conductivity. Go
ahead and interact with the applet to explore this further.


Feedback for option b:

That’s correct!

Such a semiconductor is called p type semiconductor.

There's yet another way to increase its conductivity. Go
ahead and interact with the applet to explore this further.


Feedback for option c:

If we increased the number of electrons as well as the
number of holes then recombination would take place and
this wouldn’t help in increasing the conductivity of the
crystal…Consider this and think about your options
again…


Feedback for option d:

That’s correct!

Such a semiconductor is called an extrinsic
semiconductor. And depending upon the type of impurity
added, It is called an n type or p type semiconductor.




Show the
feedback
according to the
options selected
by the user.


After displaying
the feedback.let a
radio button for
‘Explore’pop up at
the bottom right
hand side corner.


If user selects
option c let a pop
up for back also
come up..if the
user clicks on it
then go to slide 15.


When the user
clicks on it.go to
step 2.

16

Pentavalent

Impurity

Trivalent
Impurity

+

-


Si

Doping

0

max

Atomic Structure

(Display as a mouse
over)

Step
2
:

Opening page

17

Valence Band

Conduction Band

Energy Band Diagram of a
pure semiconductor

Hole

Hole

Hole

Electrons

σ

(mho/m)

N
D
(/m
3

)

-

-

-

Description of the action/ interactivity

Step
2
continued:

Instructions

18


Initially, let the screen be as indicated in slide 17.


If the user clicks on the blue rectangle without selecting the options for
Pentavalent impurity or trivalent impurity, display the Image on slide 19 in
place of the Energy band diagram.


The graph will remain blank here.


If the user clicks on Pentavalent impurity go to slide 20.


If the user clicks on Trivalent impurity go to slide 25.


If the user does not click on the button for either Pentavalent or trivalent
Impurity then the scale for Doping will remain disabled.


As soon as the user selects an option from either pentavalent or trivalent
then the scale will be enabled.



19

Atomic structure

Please include a little minus sign on the electrons...

It is not shown here due to space constraints…

electron

σ

(mho/m)

N
D
(/m
3

)

20

Valence Band

Conduction Band

Pentavalent

Impurity

Trivalent
Impurity

Atomic Structure

(Display as a mouse
over)

Step 3:

If the user selects Pentavalent Impurity

Hole

Hole

Hole

Electrons

Energy Band Diagram of a
doped semiconductor





(n type)

+

-


Si

Doping

0

max

-

-

-

Description of the action/ interactivity

Step
3
continued:

Instructions

21


Initially, when the user selects pentavalent impurity without varying the
scale(the scale should be at zero), let the screen appear as indicated.


If the user tries to vary the scale then go to next step.


If the user clicks on the blue rectangle, go to slide
24
.


If the has not varied the slider bar then the graph will not be plotted.

σ

(mho/m)

N
D
(/m
3

)

22

Valence Band

Conduction Band

Pentavalent

Impurity

Trivalent
Impurity

Atomic Structure

(Display as a mouse
over)

Step 3.1 :

Electrons

Hole

Hole

Hole

Energy Band Diagram

+

-


Si

Doping

0

max

-

-

-

-

-

-

-

-

-

-

-

-

-

Description of the action/ interactivity

Step 3.1
continued:

Instructions

Instructions for Slide
22

23


Let the slider bar for doping be enabled as soon as the user clicks on
Pentavalent Impurity.


As the user varies the slider bar from zero to max let the bulb gradually glow
brighter and let more number of electrons appear in the conduction band.


The brightness of the bulb is directly related to the number of electrons in
the conduction band..If the number of electrons in the conduction band are
more, the bulb should accordingly grow brighter.


If the user clicks on the small blue rectangle for atomic structure show the
image on the next slide in place of the energy band diagram and replace the
mouse over on the blue rectangle with Energy Band Diagram.


Repeat the animation for the atomic structure until the user clicks on the
small blue rectangle again..


As the user varies the slider bar, the graph should be plotted dynamically.


So, the graph should be plotted till the point to which the slider bar has been
dragged. If the user drags the slider bar and leaves it then the graph should
be plotted till that point to which the slider has been dragged.


Display a pop up somewhere saying:

“Other examples of donor impurities are arsenic and antimony.”


Display 12V on the power supply.



P

Free
electron

24


P

Free
electron


P

Free
electron


P

Free
electron


P

Free
electron

Please include a little minus sign on the electrons...

It is not shown here due to space constraints…

electron

σ

(mho/m)

N
A
(/m
3

)

25

Valence Band

Conduction Band

Pentavalent

Impurity

Trivalent
Impurity

Atomic Structure

(Display as a mouse
over)

Step
4
:

If the user selects Trivalent
Impurity

Hole

Hole

Hole

Electrons

Energy Band Diagram of a
doped semiconductor





(p type)

+

-


Si

Doping

0

max

-

-

-

Description of the action/ interactivity

Step
4
continued:

Instructions

26


Initially, when the user selects trivalent impurity, let the screen appear as
indicated.


If the user tries to vary the scale then go to next step.


If the user clicks on the blue rectangle, go to slide 29.


If the has not varied the slider bar then the graph will not be plotted.


σ

(mho/m)

N
A
(/m
3

)

27

Valence Band

Conduction Band

Pentavalent

Impurity

Trivalent
Impurity

Atomic Structure

(Display as a mouse
over)

Step
4.1
:

Energy Band Diagram

Holes

Electron

Electron

Electron

+

-


Si

Doping

0

max

-

-

-

Description of the action/ interactivity

Step
4.1
continued:

Instructions

Instructions for Slides 27

28


Let the slider bar for doping be enabled as soon as the user clicks on
Trivalent Impurity.


As the user varies the slider bar from zero to max let the bulb gradually glow
brighter and let more number of holes appear in the valence band.


The brightness of the bulb is directly related to the number of holes in the
valence band..If the number of holes in the valence band are more, the bulb
should accordingly grow brighter.


If the user clicks on the small blue rectangle for atomic structure show the
image on the next slide in place of the energy band diagram and replace the
mouse over on the blue rectangle with Energy Band Diagram.


Repeat the animation for the atomic structure until the user clicks on the
small blue rectangle again..


As the user varies the slider bar,the graph should be plotted dynamically.


So, the graph should be plotted till the point to which the slider bar has been
dragged. If the user drags the slider bar and leaves it then the graph should
be plotted till that point to which the slider has been dragged.


Display a pop up somewhere saying:

“Other examples of acceptor impurities are boron and gallium.”


Display
12
V on the power supply.



Al

29


Al

Al


Al

Al

hole

hole

hole

hole

hole

Please include a little minus sign on the electrons...

It is not shown here due to space constraints…

electron

Interactivity and Boundary limits


In this section, you will add the ‘Interactivity’ options to the
animation.



Use the template in the next slide to give the details.



Insert the image of the step/s (explained earlier in the
Section 3) in the box, and provide the details in the table
below.



The details of Interactivity

could be:


Types: Drop down, Slider bar, Data inputs etc.


Options: Select one, Multiple selections etc


Boundary Limits: Values of the parameters, which won’t
show results after a particular point


Results: Explain the effect of the interaction in this column



Add more slides if necessary



1

2

5

3

4

30

1

5

3

2

4

Refer to slides 15 to 29.

Instructions for the animator

Instruction
to the
learner

Results and Output

Boundary
limits

Interactivity
type
(IO
1
/IO
2
..)


Interactivity option
1
:

Step No:


31

INSTRUCTIONS SLIDE

Self
-

Assessment Questionnaire

for
Learners


Please provide a set of questions that a user
can answer based on the LO. They can be of
the following types:


These questions
should be
5
in number

and can be of
objective type (like MCQ, Match the columns, Yes or
No, Sequencing, Odd One Out).


The questions can also be open
-
ended. The user
would be asked to think about the question. The
author is requested to provide hints if possible, but a
full answer is not necessary.


One can include questions, for which the user will
need to interact with the LO (with certain
parameters) in order to answer it.

32

INSTRUCTIONS SLIDE


Please make sure that the questions can be
answered by interacting with the LO. It is
better to avoid questions based purely on
recall.

Questionnaire

for users to test their
understanding


33

Questionnaire

1
. A donor impurity has how many valence electrons?

Answers: a)

three

b)

four


c)


five

d)

six

Correct Answers:
1
)c


Feedback:


If user clicks correct answer then display
“Correct! Make sure you can explain the
reasoning!”



If user clicks incorrect answer then display

“Have a look at the atomic structure animation for
the pentavalent impurity and Try again!”

Display one question on one page..When the user selects his answer,
compare with the correct answer and display the appropriate feedback.

34

Questionnaire

Correct Answers:
2
)a


Feedback:


If user clicks correct answer then display
“Correct! Make sure you can explain the
reasoning!”



If user clicks incorrect answer then display

“Have a look at the atomic structure animation for
the trivalent impurity and Try again!”

Display one question on one page..When the user selects his answer,
compare with the correct answer and display the appropriate feedback.

35

2
. An acceptor impurity has how many valence electrons?

Answers: a)

three

b)

four


c)


five

d)

six


Feedback:


If user clicks correct answer then display “Correct! Make sure you can
explain the reasoning!”



If user clicks incorrect answer then display

“Have a look at the energy band diagrams of the n type and p type
semiconductor and try again! ”

Questionnaire

3
.What is the difference between the energy band diagram of an n type and p type semiconductor?

Answers: a)


n type semiconductor has more number of holes in the valence band as compared to the
number of electrons in the conduction band, where as p type semiconductor has more number of electrons in
the conduction band as compared to the number of holes in the valence band,

b)


n type
semiconductor has more number of electrons in the conduction band as compared to the number of holes in
the valence band, where as p type semiconductor has more number of holes in the valence band as
compared to the number of electrons in the conduction band


c)


the energy band diagrams of
n type and p type are identical
d)

n type semiconductor has more number of electrons in the conduction band
as compared to the number of holes in the valence band, where as p type semiconductor has equal number
of electron and holes in the conduction and valence band respectively.

e) p type semiconductor has more
number of holes in the valence band as compared to the number of electrons in the conduction band where
as n type semiconductor has equal number of electron and holes in the conduction and valence band
respectively.

Correct Answers:
3
)b


Display one question on one page..When the user selects his answer,
compare with the correct answer and display the appropriate feedback.

36


Feedback:


If user clicks correct answer then display “Correct! Make sure
you can explain the reasoning!”



If user clicks incorrect answer then display

“Have a look at the energy band diagrams of the n type
semiconductor and try again! ”

Questionnaire

4. What is the relation between the number of electrons and holes in the
n type semiconductor?

Answers: a)

The density of conduction band electrons in an n type
semiconductor is greater than the density of valence band holes.

b)The density of valence band holes in an n type semiconductor is
greater than the density of conduction band electrons.

c) The density of
conduction band electrons in an n type semiconductor is equal to the
density of valence band holes.

Correct Answers:
4
)a


37


Feedback:


If user clicks correct answer then display “Correct! Make sure
you can explain the reasoning!”



If user clicks incorrect answer then display

“Have a look at the energy band diagrams of the p type
semiconductor and try again! ”

Questionnaire

5
. What is the relation between the number of electrons and holes in the
p type semiconductor?

Answers: a)

The density of conduction band electrons in an p type
semiconductor is greater than the density of valence band holes.

b)The density of valence band holes in an p type semiconductor is
greater than the density of conduction band electrons.

c) The density of
conduction band electrons in an p type semiconductor is equal to the
density of valence band holes.

Correct Answers:
5
)b


38


Feedback:


If user clicks correct answer then display “Correct! Make sure
you can explain the reasoning!”



If user clicks incorrect answer then display

“Have a look at the graphs for the n type and p type
semiconductors and Try again!”

Questionnaire

6
.What happens to the conductivity of an extrinsic semiconductor as you
increase the doping?

a)Conductivity decreases as you increase the doping

b)Conductivity remains the same irrespective of the doping.

c)Conductivity increases exponentially as you increase the doping.

d)Conductivity increases as you increase the doping.

Correct Answers:
6
)d


39

Links

for further reading

Books:


1
)Solid state physics
-
MA
Wahab
.(chapter
13
)


2
)Solid state physics
-
Ashcroft/
Mermin
.
(Chapter
28
)

3
)Introduction to modern physics
-
Richtmyer
, Kennard, Cooper.(Chapter
23
)



40

INSTRUCTIONS SLIDE


Please provide points to remember to
understand the concept/ key terms of the
animation


The summary will help the user in the quick
review of the concept.

Summary


41

Summary


An Extrinsic semiconductor is one in which impurities contribute a significant
fraction of the conduction band electrons and/or valence band holes.


And depending upon the type of impurity added, It is called an n type or p type
semiconductor.


A pentavalent impurity is called a donor impurity since it supplies additional
electrons to the conduction band, and a trivalent impurity is called an acceptor
impurity since it supplies additional holes to(i.e. capture electrons from)the
valence band.


The conductivity of an extrinsic semiconductor goes on increasing with a rise in
the level of doping.

42