Difference between revisions of "PhET-Simulations-for-Physics/C3/Semiconductors/English"

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'''Semiconductors'''
 
'''Semiconductors'''
−
 
  
 
'''Author: Vidhi Thakur'''
 
'''Author: Vidhi Thakur'''
−
 
  
 
'''Keywords: PhET simulation''', dopants, diode, valence band, conduction band, donor, acceptor, depletion region '''video tutorial.'''
 
'''Keywords: PhET simulation''', dopants, diode, valence band, conduction band, donor, acceptor, depletion region '''video tutorial.'''
Line 23: Line 21:
  
 
|| In this tutorial, we will learn,
 
|| In this tutorial, we will learn,
−
 
  
 
* How a battery acts as a driving force in a circuit.
 
* How a battery acts as a driving force in a circuit.
 
* To add dopants to move the electrons in the circuit.
 
* To add dopants to move the electrons in the circuit.
−
* How the dopants change energy levels in a semiconductor
+
* How the dopants change energy levels in a semiconductor.
−
* Why a pn junction acts as a diode
+
−
* Why a depletion region does not allow current to flow.
+
  
 +
|-
  
−
|-
 
 
|| '''Slide Number 3'''
 
|| '''Slide Number 3'''
  
−
'''System Requirement'''
+
'''Learning Objectives'''
−
|| Here I am using
+
  
 +
||
 +
* Why a pn junction acts as a diode.
 +
* Why a depletion region does not allow current to flow.
 +
|-
  
−
*'''Windows 11 (64 bit)'''.
+
|| '''Slide Number 4'''
  
−
*'''Java Version 1.8'''.
+
'''System Requirement'''
 +
|| Here I am using,
 +
 
 +
* '''Windows 11 (64 bit)'''.
 +
* '''Java version 1.8'''.
 
|-
 
|-
−
||'''Slide Number 4'''
+
||'''Slide Number 5'''
  
 
'''Pre-requisites'''
 
'''Pre-requisites'''
 
'''https://spoken-tutorial.org'''
 
'''https://spoken-tutorial.org'''
 
||To follow this tutorial the learner should be familiar with topics in high school science.
 
||To follow this tutorial the learner should be familiar with topics in high school science.
 +
 
Please use the link below to access the tutorials on PhET simulations.
 
Please use the link below to access the tutorials on PhET simulations.
 
|-
 
|-
−
||'''Slide Number 5'''
+
||'''Slide Number 6'''
−
 
+
−
'''Link for PhET simulation'''
+
−
 
+
−
point to
+
  
 +
'''Link for PhET simulation''' point to
  
 
'''https://phet.colorado.edu/en/simulations/conductivity/about'''
 
'''https://phet.colorado.edu/en/simulations/conductivity/about'''
−
|| Please use the given link to download the PhET simulation.
+
|| Please use the given link to download the '''PhET simulation'''.
  
  
Line 71: Line 71:
 
|-  
 
|-  
 
||'''Cursor on the interface.'''
 
||'''Cursor on the interface.'''
−
|| This is the interface of '''Semiconductors simulation.'''
+
|| This is the interface of '''Semiconductors simulation'''.
 
|-
 
|-
 
||Cursor on '''main panel'''.
 
||Cursor on '''main panel'''.
Line 77: Line 77:
  
 
Cursor on '''input box.'''
 
Cursor on '''input box.'''
−
 
−
 
−
Cursor on '''electrons.'''
 
−
 
 
|| The main panel consists of a circuit.
 
|| The main panel consists of a circuit.
  
Line 86: Line 82:
 
The circuit has a battery with the box to input the voltage.
 
The circuit has a battery with the box to input the voltage.
  
−
 
+
|-
−
'''Electrons''' are represented as blue spheres in the circuit.
+
||Cursor on '''electrons.'''
 +
||'''Electrons''' are represented as blue spheres in the circuit.
 
|-
 
|-
 
|| Cursor on '''dopants.'''
 
|| Cursor on '''dopants.'''
 +
|| Two blank spaces are provided in the circuit to add two dopants.
  
−
|| Point to the P Type and N Type dopants at the bottom.
 
 
A dopant is an impurity added to semiconductors to modify their conductivity.
 
A dopant is an impurity added to semiconductors to modify their conductivity.
  
 +
|-
 +
||Point to the P Type and N Type dopants at the bottom.
 +
||A '''P-Type''' dopant is represented as red spheres and '''N-Type''' as green spheres.
  
−
At the bottom right P-type dopant is represented as '''red''' spheres and N-type as '''green''' spheres.
+
'''P-type''' dopant is with more holes, whereas '''N-type''' dopant is with more electrons.
−
 
+
−
 
+
−
A P Type dopant is represented as '''red''' spheres and N Type as '''green''' spheres.
+
−
 
+
−
 
+
−
P-type dopant is with more holes, whereas n-type dopant is with more electrons.
+
−
 
+
−
 
+
  
 
|-
 
|-
Line 112: Line 104:
  
  
−
It expands into bands represented as '''yellow rectangles''' on the left panel.
+
It expands into bands represented as yellow rectangles on the left panel.
  
  
−
The low energy band is the''' valence''' band.
+
The low energy band is the '''valence''' band.
  
  
 
It is filled with blue spheres as electrons and plus signs as holes.
 
It is filled with blue spheres as electrons and plus signs as holes.
−
 
−
 
  
 
|-
 
|-
−
||  
+
|| Cursor on '''conduction''' band.
−
 
+
−
Cursor on '''conduction''' band.
+
 
|| The high energy band is the '''conduction''' band.
 
|| The high energy band is the '''conduction''' band.
  
Line 132: Line 120:
  
  
−
'''Internal force '''arrow gives us the direction of the internal force.
+
'''Internal force''' arrow gives us the direction of the internal force.
  
  
−
'''Battery force '''arrow''' '''gives us the direction of battery force.
+
'''Battery force ''' arrow gives us the direction of battery force.
 
|-
 
|-
 
|| Cursor on right panel.
 
|| Cursor on right panel.
Line 144: Line 132:
  
 
'''Two(2)''' Segments.  
 
'''Two(2)''' Segments.  
−
 
−
 
  
 
|| On the right panel the '''Segments''' section is present.
 
|| On the right panel the '''Segments''' section is present.
  
−
It consists of one and two as options.
+
It consists of '''one''' and '''two''' as options.
  
  
−
The''' one(1) '''Segment provides space for one dopant only.
+
The ''' one(1)''' segment provides space for one dopant only.
−
 
+
−
The '''two(2)''' Segments provide space for two segments.
+
−
 
+
  
 +
The '''two(2)''' segments provide space for two dopants.
  
 
|-
 
|-
 
|| Click on segment '''one'''.
 
|| Click on segment '''one'''.
−
 
−
 
−
Cursor on bands.
 
−
 
−
 
 
|| Let us first select segment one(1).  
 
|| Let us first select segment one(1).  
  
 
Here only one segment is present.
 
Here only one segment is present.
  
 +
|-
 +
||Cursor on bands.
 +
||The electrode attached to the dopant expands into bands with electrons and holes.
  
−
The electrode attached to the dopant expands into bands with electrons and holes.
 
  
 +
Lower energy band is the '''valence''' band with low energy.
  
−
Lower energy band is the valence band with low energy.
+
The higher energy band is the '''conduction''' band with high energy.
−
 
+
−
The higher energy band is the conduction band with high energy.
+
−
 
+
  
 
|-
 
|-
Line 183: Line 162:
  
 
Click on the up arrow till '''4V'''.
 
Click on the up arrow till '''4V'''.
−
 
−
 
−
 
  
 
Cursor on circuit diagram.
 
Cursor on circuit diagram.
−
|| Let’s drag and place a '''P-type '''dopant to fill in the purple space in the circuit.
+
|| Let’s drag and place a '''P-type ''' dopant to fill in the purple space in the circuit.
−
 
+
−
 
+
  
  
Line 196: Line 170:
  
  
−
Current flows in the circuit with low energy from left-right.
+
Current flows in the circuit with low energy from left to right.
 
|-
 
|-
 
|| Click on down arrow till '''-4V.'''
 
|| Click on down arrow till '''-4V.'''
−
|| Now let us decrease the voltage to''' -4 volts'''.
+
|| Now let us decrease the voltage to ''' -4 volts'''.
  
  
Line 205: Line 179:
  
  
−
There is a flow of current in the right-left direction in the circuit.
+
There is a flow of current in the right to left direction in the circuit.
  
  
Line 215: Line 189:
 
|-
 
|-
 
|| Click on '''Clear Dopants'''.
 
|| Click on '''Clear Dopants'''.
 +
|| Let us clear the dopants.
 +
|-
 +
||Drag and add '''N-type''' dopant and click up arrow till 4V.
  
 +
||Add '''N-type''' dopant to the space and increase the voltage to '''4 volts'''.
  
−
Drag and add '''N-type''' dopant and click up arrow till 4V.
 
  
 +
Since '''N-type''' dopants have more electrons they are known as '''donors'''.
  
  
−
|| Let us clear dopants now.
+
The flow of current is from left to right in the '''conduction''' band at high energy.
−
 
+
−
 
+
−
Add N-type dopant to the space and increase the voltage to '''4 volts'''.
+
−
 
+
−
 
+
−
Since N-type dopants have more electrons they are known as '''donors'''.
+
−
 
+
−
 
+
−
The flow of current is from left to right in the conduction band at high energy.
+
−
 
+
−
 
+
  
 
|-
 
|-
−
||  
+
|| Click the down arrow till -4V.
−
 
+
|| Now let us change the voltage to ''' -4 ''', that is, change the terminal of the battery.
−
Click the down arrow till -4V.
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
||  
+
−
 
+
−
Now let us change the voltage to''' -4 ''', that is. change the terminal of the battery.
+
−
 
+
−
 
+
−
This time flow of current is in the right-left''' '''direction
+
−
 
+
−
in the conduction band.
+
  
  
 +
This time flow of current is in the right to left direction in the '''conduction''' band.
  
 
|-
 
|-
 
|| Click on '''two''' segment.
 
|| Click on '''two''' segment.
−
 
+
|| Now let us select segments '''two(2)'''.
−
 
+
|-
−
Drag and add '''P-type''' dopant in the left space.
+
||Drag and add '''P-type''' dopant in the left space.
  
 
Click the arrow till 4V.
 
Click the arrow till 4V.
  
  
−
Cursor on internal force and battery force.
+
||Drag and add '''P-type''' dopant in the left space and increase the voltage to 4 volts.
−
|| Now let us select Segments '''two(2)'''.
+
  
  
−
Drag and add '''P-type''' dopant in the left space and increase the voltage to 4 volts.
+
Note that electrons and holes in the '''valence''' band of the left segment disappear.
  
 +
This is because '''P-type''' dopant is an acceptor.
  
−
Note that electrons and holes in the valence band of the left segment disappear.
+
|-
−
 
+
||Cursor on internal force and battery force.
−
This is because p-type dopant is an acceptor.
+
||Internal force is zero and battery force is from left to right.
−
 
+
−
 
+
−
Internal force is zero and battery force is from left to right.
+
  
 
So, there is no flow of current in the circuit.
 
So, there is no flow of current in the circuit.
Line 285: Line 232:
 
|-
 
|-
 
|| Drag and add an '''N-type''' dopant in the right space.
 
|| Drag and add an '''N-type''' dopant in the right space.
−
 
+
|| Let us drag and add an '''N-type''' dopant in the right space.
−
 
+
−
 
+
−
 
+
−
Cursor on battery.
+
−
 
+
−
 
+
−
 
+
−
|| Let us drag and add an N-type dopant in the right space.
+
  
  
 
Such diode formation is known as '''pn''' junction diode.
 
Such diode formation is known as '''pn''' junction diode.
  
 +
|-
 +
||Cursor on battery.
 +
||Here the positive terminal of the battery is connected to '''N-type'''.
  
−
Here the positive terminal of the battery is connected to N-type.
+
Negative terminal is connected to the '''P-type'''.
−
 
+
−
Negative terminal is connected to the P-type.
+
−
 
+
−
 
+
−
Such arrangement is known as '''reversed bias.'''
+
  
  
 +
Such arrangement is known as '''reversed bias'''.
  
 
|-
 
|-
−
|| Cursor on valence band and conduction band.
+
|| Cursor on '''valence''' band and '''conduction''' band.
 
|| Empty space is filled by electrons in the '''P-type''' dopant.
 
|| Empty space is filled by electrons in the '''P-type''' dopant.
  
  
−
And holes occupy the conduction band of '''N-type''' dopant.
+
And holes occupy the '''conduction''' band of '''N-type''' dopant.
  
  
−
The direction of internal force, and battery force, are in the same''' '''direction.
+
The direction of internal force, and battery force, are in the same direction.
  
  
Line 322: Line 260:
  
  
−
This is due to the diffusion of carriers across the junction of the pn diode.
+
This is due to the diffusion of carriers across the junction of the '''pn''' diode.
−
 
+
−
 
+
  
  
 
So, no flow of current is observed.
 
So, no flow of current is observed.
−
 
−
 
  
 
|-
 
|-
Line 344: Line 278:
  
  
−
At -4 Volts the battery force changes the direction and internal force becomes zero.
+
At '''-4 Volts''' the battery force changes the direction and internal force becomes zero.
  
  
−
At -4 Volts, P-type dopant is connected to the positive terminal and vice-versa.
+
At '''-4 Volts''', '''P-type''' dopant is connected to the positive terminal and vice-versa.
  
  
Line 353: Line 287:
  
  
−
So, current flow is seen from N-type to P-type '''dopant '''in''' '''right-left direction.
+
So, current flow is seen from '''N-type''' to '''P-type ''' dopant in right to left direction.
−
 
+
−
 
+
  
 
|-
 
|-
Line 363: Line 295:
 
Drag and add '''N-type''' dopant in left space and click up arrow till 4V.
 
Drag and add '''N-type''' dopant in left space and click up arrow till 4V.
  
−
 
+
|| Now let's clear the '''dopants'''.
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
 
+
−
Cursor on battery and internal force.
+
−
|| Now let”s clear the '''dopants'''.
+
  
  
Line 377: Line 301:
  
  
−
Electrons and holes are visible in the left segment as N-type dopants are donors.
+
Electrons and holes are visible in the left segment as '''N-type''' dopants are donors.
  
 +
|-
 +
||Cursor on battery and internal force.
 +
||'''Internal force''' is zero and battery force is in the right direction.
  
  
−
 
+
So, there is no flow of current.
−
'''Internal''' '''force''' is zero and battery force is in the right direction.
+
−
 
+
−
 
+
−
So, there is no flow of current,''' '''
+
−
 
+
−
 
+
  
 
|-
 
|-
−
|| Drag and add a P-type dopant in the right space.
+
|| Drag and add a '''P-type''' dopant in the right space.
  
 
Cursor on battery
 
Cursor on battery
−
 
−
 
−
 
  
 
|| Let us drag and add '''P-type '''dopant in the right segment.
 
|| Let us drag and add '''P-type '''dopant in the right segment.
  
  
−
Such diode formation is known as '''pn junction diode'''.
+
Such diode formation is known as '''pn''' junction diode.
  
  
−
Here, positive terminal is connected to P-type and negative terminal to N-type.
+
Here, positive terminal is connected to '''P-type''' and negative terminal to '''N-type'''.
  
  
−
Such an arrangement is known as''' forward bias.'''
+
Such an arrangement is known as ''' forward bias.'''
  
  
−
Flow of current is seen from N-type to P-type dopant from left to right direction.
+
Flow of current is seen from '''N-type''' to '''P-type''' dopant from left to right direction.
  
  
Line 415: Line 333:
 
|-
 
|-
 
|| Click on down arrow till '''-4V'''.
 
|| Click on down arrow till '''-4V'''.
 +
|| I will now change the voltage to ''' -4 Volts'''.
  
  
−
 
+
The electrons in the left segment of the '''conduction''' band disappear.
−
|| I will now change the voltage to''' -4 Volts'''.
+
−
 
+
−
 
+
−
The electrons in the left segment of the conduction band disappear.
+
  
 
Only holes are left.
 
Only holes are left.
−
 
−
 
−
 
  
 
Internal force and battery force are in the left direction.
 
Internal force and battery force are in the left direction.
  
 
So, we see no flow of current.
 
So, we see no flow of current.
−
 
−
 
  
 
|-
 
|-
−
|| '''Slide Number 6'''
+
|| '''Slide Number 7'''
  
 
'''Summary'''
 
'''Summary'''
Line 443: Line 353:
  
  
−
In this tutorial we have learnt,* How a battery acts as a driving force in a circuit.
+
In this tutorial we have learnt,
 +
* How a battery acts as a driving force in a circuit.
 
* To add dopants to move the electrons in the circuit.
 
* To add dopants to move the electrons in the circuit.
−
* How the dopants change energy levels in a semiconductor
+
* How the dopants change energy levels in a semiconductor.
−
* Why a pn junction acts as a diode
+
 
 +
 
 +
|-
 +
 
 +
|| '''Slide Number 8'''
 +
 
 +
'''Summary'''
 +
||
 +
* Why a pn junction acts as a diode.
 
* Why a depletion region does not allow current to flow.
 
* Why a depletion region does not allow current to flow.
  
 
|-
 
|-
−
|| '''Slide Number 7'''
+
|| '''Slide Number 9'''
  
 
'''Assignment'''
 
'''Assignment'''
−
||  
+
|| As an assignment,
  
−
As an assignment,
+
* Make various combinations of dopants at different voltages and record the observations.
−
 
+
−
Make various combinations of dopants at different voltages and record the observations.
+
  
 
|-
 
|-
−
|| '''Slide''': 8
+
|| '''Slide Number 10'''
  
 
'''About Spoken Tutorial Project '''
 
'''About Spoken Tutorial Project '''
 
||The video at the following link summarizes the Spoken Tutorial project.  
 
||The video at the following link summarizes the Spoken Tutorial project.  
−
* Please download and watch it.
 
  
 +
Please download and watch it.
  
 
|-
 
|-
−
|| '''Slide''': 9
+
|| '''Slide Number 11'''
  
 
'''Spoken tutorial workshops '''
 
'''Spoken tutorial workshops '''
 
||We conduct workshops using spoken tutorials and give certificates.  
 
||We conduct workshops using spoken tutorials and give certificates.  
−
* For more details, please contact us.
 
  
 +
For more details, please contact us.
  
 
|-
 
|-
−
|| '''Slide''': 10
+
|| '''Slide Number 12'''
  
 
'''Answers for THIS Spoken Tutorial '''
 
'''Answers for THIS Spoken Tutorial '''
−
 
+
|| Please post your timed queries in this forum.
−
Do you have questions in THIS Spoken Tutorial?
+
−
 
+
−
Please visit this site
+
−
 
+
−
Choose the minute and second where you have the question.
+
−
 
+
−
Explain your question briefly
+
−
 
+
−
The spoken tutorial project will ensure answer.
+
−
 
+
−
You will have to register on this website to ask questions.
+
−
|| * <div style="margin-left:1.245cm;margin-right:0cm;">Please post your timed queries in this forum.
+
−
 
+
  
 
|-
 
|-
−
|| '''Slide''': 11
+
|| '''Slide Number 13'''
−
 
+
−
'''Forum '''
+
−
||The Spoken Tutorial forum is for specific questions on this tutorial.
+
−
* Please do not post unrelated and general questions on them.
+
−
* This will help reduce the clutter.
+
−
* With less clutter, we can use these discussions as instructional material.
+
−
 
+
−
 
+
−
|-
+
−
|| '''Slide''': 12
+
  
 
'''Acknowledgement '''
 
'''Acknowledgement '''
 
|| Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India  
 
|| Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India  
 
|-
 
|-
−
||  
+
|| '''Slide Number 14'''
−
||This is Vidhi Thakur, a FOSSEE
+
−
* summer fellow 2022, IIT Bombay
+
−
* signing off
+
  
 +
'''Thank you'''
  
 +
||This is Vidhi Thakur, a FOSSEE summer fellow 2022, IIT Bombay signing off.
  
 
Thank you for joining.
 
Thank you for joining.
 
|-
 
|-
 
|}
 
|}
−
 
−
 
−
<div style="margin-left:0.811cm;margin-right:0cm;">
 

Latest revision as of 15:25, 10 January 2023

Semiconductors

Author: Vidhi Thakur

Keywords: PhET simulation, dopants, diode, valence band, conduction band, donor, acceptor, depletion region video tutorial.


Visual Cue Narration
Slide Number 1

Title Slide

Welcome to this spoken tutorial on Semiconductors.
Slide Number 2

Learning Objectives

In this tutorial, we will learn,
  • How a battery acts as a driving force in a circuit.
  • To add dopants to move the electrons in the circuit.
  • How the dopants change energy levels in a semiconductor.
Slide Number 3

Learning Objectives

  • Why a pn junction acts as a diode.
  • Why a depletion region does not allow current to flow.
Slide Number 4

System Requirement

Here I am using,
  • Windows 11 (64 bit).
  • Java version 1.8.
Slide Number 5

Pre-requisites https://spoken-tutorial.org

To follow this tutorial the learner should be familiar with topics in high school science.

Please use the link below to access the tutorials on PhET simulations.

Slide Number 6

Link for PhET simulation point to

https://phet.colorado.edu/en/simulations/conductivity/about

Please use the given link to download the PhET simulation.


https://phet.colorado.edu/en/simulations/semiconductor/about

Point to the file in the Downloads folder. I have downloaded the Semiconductors simulation to my Downloads folder.
Double click the file to open To open the simulation double click on the file.
Cursor on the interface. This is the interface of Semiconductors simulation.
Cursor on main panel.


Cursor on input box.

The main panel consists of a circuit.


The circuit has a battery with the box to input the voltage.

Cursor on electrons. Electrons are represented as blue spheres in the circuit.
Cursor on dopants. Two blank spaces are provided in the circuit to add two dopants.

A dopant is an impurity added to semiconductors to modify their conductivity.

Point to the P Type and N Type dopants at the bottom. A P-Type dopant is represented as red spheres and N-Type as green spheres.

P-type dopant is with more holes, whereas N-type dopant is with more electrons.

Cursor on dopant.

Cursor on valence band.

An electrode is connected to each dopant.


It expands into bands represented as yellow rectangles on the left panel.


The low energy band is the valence band.


It is filled with blue spheres as electrons and plus signs as holes.

Cursor on conduction band. The high energy band is the conduction band.


In semiconductors the gap between the bands is small.


Internal force arrow gives us the direction of the internal force.


Battery force arrow gives us the direction of battery force.

Cursor on right panel.


Point to one(1) Segment.


Two(2) Segments.

On the right panel the Segments section is present.

It consists of one and two as options.


The one(1) segment provides space for one dopant only.

The two(2) segments provide space for two dopants.

Click on segment one. Let us first select segment one(1).

Here only one segment is present.

Cursor on bands. The electrode attached to the dopant expands into bands with electrons and holes.


Lower energy band is the valence band with low energy.

The higher energy band is the conduction band with high energy.

Drag and add P-type in space in the bottom of the circuit.


Click on the up arrow till 4V.

Cursor on circuit diagram.

Let’s drag and place a P-type dopant to fill in the purple space in the circuit.


Increase the voltage to 4 volts and observe the movement of electrons in the circuit.


Current flows in the circuit with low energy from left to right.

Click on down arrow till -4V. Now let us decrease the voltage to -4 volts.


This way we change the terminals of the battery in the opposite direction.


There is a flow of current in the right to left direction in the circuit.


Changing the terminals, changes the direction of potential difference.


Hence direction of flow of current changes.

Click on Clear Dopants. Let us clear the dopants.
Drag and add N-type dopant and click up arrow till 4V. Add N-type dopant to the space and increase the voltage to 4 volts.


Since N-type dopants have more electrons they are known as donors.


The flow of current is from left to right in the conduction band at high energy.

Click the down arrow till -4V. Now let us change the voltage to -4 , that is, change the terminal of the battery.


This time flow of current is in the right to left direction in the conduction band.

Click on two segment. Now let us select segments two(2).
Drag and add P-type dopant in the left space.

Click the arrow till 4V.


Drag and add P-type dopant in the left space and increase the voltage to 4 volts.


Note that electrons and holes in the valence band of the left segment disappear.

This is because P-type dopant is an acceptor.

Cursor on internal force and battery force. Internal force is zero and battery force is from left to right.

So, there is no flow of current in the circuit.

Drag and add an N-type dopant in the right space. Let us drag and add an N-type dopant in the right space.


Such diode formation is known as pn junction diode.

Cursor on battery. Here the positive terminal of the battery is connected to N-type.

Negative terminal is connected to the P-type.


Such arrangement is known as reversed bias.

Cursor on valence band and conduction band. Empty space is filled by electrons in the P-type dopant.


And holes occupy the conduction band of N-type dopant.


The direction of internal force, and battery force, are in the same direction.


Hence a more resistive thicker depletion region is formed.


This is due to the diffusion of carriers across the junction of the pn diode.


So, no flow of current is observed.

Click on down arrow till -4V.


Cursor on battery and internal force.

Cursor on battery.

Now let us slowly change the voltage to -4 Volts.


Notice that decrease in voltage decreases the size of the battery force arrow.


At -4 Volts the battery force changes the direction and internal force becomes zero.


At -4 Volts, P-type dopant is connected to the positive terminal and vice-versa.


Hence it is forward biased, so the depletion region is thinner here.


So, current flow is seen from N-type to P-type dopant in right to left direction.

Click on Clear Dopants.


Drag and add N-type dopant in left space and click up arrow till 4V.

Now let's clear the dopants.


Drag and add N-type dopant in the left space and increase the voltage to 4 Volts.


Electrons and holes are visible in the left segment as N-type dopants are donors.

Cursor on battery and internal force. Internal force is zero and battery force is in the right direction.


So, there is no flow of current.

Drag and add a P-type dopant in the right space.

Cursor on battery

Let us drag and add P-type dopant in the right segment.


Such diode formation is known as pn junction diode.


Here, positive terminal is connected to P-type and negative terminal to N-type.


Such an arrangement is known as forward bias.


Flow of current is seen from N-type to P-type dopant from left to right direction.


Battery force is also in the same direction.

Click on down arrow till -4V. I will now change the voltage to -4 Volts.


The electrons in the left segment of the conduction band disappear.

Only holes are left.

Internal force and battery force are in the left direction.

So, we see no flow of current.

Slide Number 7

Summary

With this we come to the end of this tutorial.

Let's summarise.


In this tutorial we have learnt,

  • How a battery acts as a driving force in a circuit.
  • To add dopants to move the electrons in the circuit.
  • How the dopants change energy levels in a semiconductor.


Slide Number 8

Summary

  • Why a pn junction acts as a diode.
  • Why a depletion region does not allow current to flow.
Slide Number 9

Assignment

As an assignment,
  • Make various combinations of dopants at different voltages and record the observations.
Slide Number 10

About Spoken Tutorial Project

The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

Slide Number 11

Spoken tutorial workshops

We conduct workshops using spoken tutorials and give certificates.

For more details, please contact us.

Slide Number 12

Answers for THIS Spoken Tutorial

Please post your timed queries in this forum.
Slide Number 13

Acknowledgement

Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India
Slide Number 14

Thank you

This is Vidhi Thakur, a FOSSEE summer fellow 2022, IIT Bombay signing off.

Thank you for joining.

Contributors and Content Editors

Madhurig, Nancyvarkey, Vidhithakur

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