Physics Semiconductors Project

9/22/2015

Physics sem iconductor s pr oject

SlideShare Explore Search You

Upload Upload Login Signup Sig nup

Search Se arch

Home Home Technology Education Ed ucation More Mo re Topics Topics For Uploaders For Uploaders Collect Leads Get Started Tipss & Tricks Tip Tools To ols Forr Business Fo Search

Semiconductors… Physics Project..

http://www.sli deshar e.net/Aashir w adJi ndal /physics- sem i conductor s- pr oj ect

1/25

9/22/2015

Physics sem iconductor s pr oject

Aashirwad ‐ Aashirwad jindal

4 of 27

to

– heema mam

“If we knew what it was we were doing, it would not be called research, would it?” ― Albert Einstein

1 | p h y s i c s p r o j e c t .

Welcome to this basic tour of semiconductor physics! Two of our most excellent guides, Sally Con and Jerry Manium, will take you through. http://www.sli deshar e.net/Aashir w adJi ndal /physics- sem i conductor s- pr oj ect

2/25

9/22/2015

Physics semiconductors project

Sally and Jerry explain things in different ways. Sally tries to be correct, and likes to stick to the facts. Jerry is easy-going, and uses examples from the everyday world around us. let Sally and Jerry explain a few things!

Physics semiconductors project 31,640 Share Like Download

Aashirwad Jindal, schooling at school Follow 0

0

0

0

Published on Jan 31, 2014

its a complete project on semi conductors ...u just ned to save it and have fun its perfect at its ...


Published in: Technology, Business 3 Comments 26 Likes Statistics Notes Introduction…

Full Name Comment goes here. 12 hours ago Delete Reply Spam Block Are you sure you want to Yes No Your message goes here

Share your thoughts... Post

Vishal Trivedi , C.E.O. at Nike @Kshitij Sharma ......Idiot or what you don know how to download!! http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

3/25

9/22/2015


3 weeks ago Reply Are you sure you want to Yes No Your message goes here

Kshitij Sharma please allow us to download this..... 9 months ago Reply Are you sure you want to Yes No Your message goes here

Syed Rizwan Yasin , Manager at Android/IOS helpdesk - Indian Dats a good one bro 11 months ago Reply Are you sure you want to Yes No | p h y s i c goes s p r ohere j ec t . Your 3message

aishuapte 2 weeks ago

History..

Vishal Trivedi , C.E.O. at Nike 3 weeks ago

Jhapranav 1 month ago

Let's begin this journey into the world of semiconductors with a look at the history books. In the early 1900s, not much was known of the world at an atomic level, and even less so at the subatomic level. Physics, to a large extent, still calmly followed classical rules. But new discoveries Harit Sharma like Röntgen's x rays, Thomson's electron and Rutherford's discovery 2 months ago of the atomic nucleus made it clear that new rules were needed. Scientists like Planck, Einstein, Bohr,Pauli and Heisenberg, to name a few, all contributed to the development and understanding necessary for the creation of the new paradigm of quantum physics. The development of vermaakash1999quantum physics also laid the ground for 'Solid State Physics' which is a 3 months ago discipline explaining the internal atomic structure and the electronic properties of the materials that we see in our everyday life such as metals, plastics, glass, etc. Show More

No Downloads Views Total Views 31,640 http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

4/25

9/22/2015

On Slideshare 0 From Embeds 0 Number of Embeds 0 Actions Shares 0 Downloads 1,411 Comments 3 4 | p h y s i c s Likes 26 Embeds 0 No embeds


p r o j ec t .

No notes for slide

History.. [Type sidebar content. A sidebar is a standalone supplement to the main document. Physics semiconductors projectIt is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab 1. 1. Semiconductors… Physics Project.. of -Aashirwad jindal to –box.] heema mam “If we knew what it was to change the formatting the sidebar text

we were doing, it would not be called research, would it?” ― Albert Einstein 1|physics project. 2. 2. Welcome to this basic tour of semiconductor physics! Two of our most excellent guides, Sally Con and Jerry Manium, will take you through. Sally and Jerry explain things in different ways. Sally tries to be correct, and likes to stick to the facts. Jerry is easy-going, and uses examples from the everyday world around us. let Sally and Jerry explain a few things! 2|physics project. 3. 3. Introduction… 3|physics project. 4. 4. History.. Let's begin this journey into the world of semiconductors with a look at the history books. In the early 1900s, not much was known of the world at an atomic level, and even less so at the subatomic level. Physics, to a large extent, still calmly followed classical rules. But new discoveries like Röntgen's x-rays, Thomson's electron and Rutherford's discovery of the atomic nucleus made it clear that new rules were needed. Scientists like Planck, Einstein, Bohr,Pauli and Heisenberg, to name a few, all contributed to the development and understanding necessary for the creation of the new paradigm of quantum physics. The development of quantum physics also laid the ground for 'Solid State Physics' which is a discipline explaining the internal atomic structure and the electronic properties of the materials that we see in our everyday life such as metals, plastics, glass, etc. 4|physics project. 5. 5. History.. [Type sidebar content. A sidebar is a standalone supplement to the main document. It is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab to change the formatting of the sidebar text box.] 5|physics project. 6. 6. Electricity Before we start, it would be a good idea to clarify what electricity is. Electricity can be seen as a stream of electrons. Electrons are tiny particles with a negative charge. So, roughly explained, electricity is a stream of electrons flowing from one point to another. A good way to explain an electric current passing through a cable would be to imagine a pipe filled with marbles that exactly fit the pipe. If we push a marble into the pipe in one end, the motion would be distributed, each marble pushing its neighbor, so that almost instantly a marble in the other end would be pushed out of the pipe. 6|physics project.

http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

5/25

9/22/2015


7. 7. Conductivity..!! [Type sidebar content. A sidebar is a standalone supplement to the main document. It is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab to change the formatting of the sidebar text box.] 7|physics project. 8. 8. Why semiconductors..??? 8|physics project. 9. 9. Semiconducting materials..!! Semiconductors can be made of a single material or a combination of several different materials. In early semiconductor devices germanium was often used. However in today's semiconductor industry, silicon is commonly used. Silicon is very easy to find in Nature. Ordinary sand, like on the beach or in the desert for example, is nothing more than one silicon 5 | p h y s i c s p r o j e c t . atom combined with two oxygen atoms. However, if you want silicon in its pure form suitable for the production of, for instance, computer chips it has to be purified in a carefully monitored process. One of the main reasons for the popularity of silicon is that it is stable and can be heated to a rather high degree without loosing its material characteristics. This means that engineers can be sure it will perform according to their plans, even under quite extreme conditions. 9|physics project. 10. 10. Semiconducting materials cont…. [Type sidebar content. A sidebar is a standalone supplement to the main document. It is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab to change the formatting of the sidebar text box.] Just to make sure we avoid misunderstandings, when we talk about silicon, we don't mean silicone spelled with an "e" at the end, 'cause that is a material mostly known for its use in human implants. To understand the principles of semiconductors, it is good to first understand the basics of atoms and energy levels within atoms. So that's where we're going to start. 10 | p h y s i c s p r o j e c t . 11. 11. Silicon and its molecules.. If we look at the solid material of Silicon we will see that it is built from a huge numberBefore of Silicon atomsitthat are brought together. atoms interact with each we start, would be a good idea to When clarifythe what other, the atomic shells of eachis. atom interactscan with atomic shells ofofneighboring atoms. On an electricity Electricity bethe seen as a stream energy scale, the overlapping shells all particles the separate form energy bands that are electrons.energy Electrons areoftiny withatoms a negative similar to the energycharge. shells in theroughly single atom. Between the bands electrons So, explained, electricity is ano stream of are allowed. In a simplified way, it is electrons almost as flowing if the solid material is antoenlargement of the single atom. 11 | p h y s from one point another. icsproject. 12. 12. Bands and their theories... To continue our journey, you don't need to fully understand what Sally just said. But what you do need to understand is, that the highest energy band that is occupied by electrons in a material is called the valence band, just like in the single atom where the highest shell occupied by electrons is called the valence shell. The band with energy one step higher than the valence band is theconduction band. The energy gap between these two bands, where no electrons are allowed, is called the band gap. If you think of the energy bands as steps in a staircase then the band gap is the area between the steps. You can put your foot on the first step of the stairs and you can put it on the second, but you can never put it 12 | p h y s i c s p r o j e c t . 13. 13. Bands and their theories... cont… somewhere between the first and second. 13 | p h y s i c s p r oject. 14. 14. A electron-hole pair..!! A very important feature of the semiconductor material is the electronA good way to explain an electric current passing through a hole pair. To get a semiconductor to conduct a current, we must make an electron jump from an cable would to imagine marbles thatempty state). This occupied to an unoccupied energybelevel. When ita pipe does filled this it with leaves a hole (an the pipe. If weitself pushleaves a marble intohole. the pipe in onewe could say that hole can be filled byexactly anotherfit electron, which a new Therefore, the motion would marble pushing both the hole and theend, electron contribute to be thedistributed, conductivityeach as they move around in the material. its neighbor, so that almost instantly a marble in the other The hole is like a positive charge (lack of negative), the electron is negative. It's a little bit like this would pushed outaround of theto pipe. simple puzzle game end where you be move pieces form an image. The moving pieces correspond to the electrons, of course. 14 | p h y s i c s p r o j e c t . 15. 15. Conduction in different types of materials… As mentioned earlier, the semiconductor has a conducting capacity somewhere between the conductor and the insulator. If we look closer at the materials we can see why they behave like this. Before we go on, note that contrary to what its name may suggest, the conduction band is not the only band where conduction of a current may

Electricity


6/25

9/22/2015


occur. Conduction is equally possible in the valence band. In a good conductor like a metal, the highest energy band with electrons (valence band) is only partially filled. This means that the electrons 6 | p hcan y s i accelerate. c s p r o j e c tIn . other words, they gain energy so that they can transfer to 15 | p h y s i c sproject. 16. 16. Conduction in different types of materials… higher energy levels that are empty. Simply put, in a conductor there is plenty of room for the electrons to jump from an occupied state to an empty one. If you felt that Sally's explanation of the conduction properties in different materials was crystal clear, you can skip the following part. But if you're still a little unsure of how it works, I will try to show you another way of looking at this phenomenon. To help my explanation, I am going to Conductivity..!! use thesidebar unrealistic cup withAthe water-filled compartments again. The compartments equal [Type content. sidebar is a standalone supplement to the energy bands of the material and the water 16 | p h y s i c s p r o j e c t . the main document. It is often aligned on the left or right of the 17. 17. Conduction in different types of materials… equals the electrons. This time the cup only has page, or located at the topband or bottom. Usethe the Text Boxband. Tools two compartments, one for the valence and one for conduction In tab a conductor, the valence band is only the partially filled. This that, in text our cup, we are going to have the valence to change formatting of means the sidebar box.] compartment half-filled with water. If we tip the cup from side to side, we will see that it is easy for the water to move back and forth, just as it is easy for the electrons to move within the conductor. A semiconductor at low temperature is an insulator because there is no place for the electrons to go to. The valence compartment is filled and no matter how we tip the cup there is no room for the water to move into. At room temperature, the heat (energy) makes the atoms vibrate slightly, enough for a few of the electrons to break their bonds and jump into the 17 | p h y s i c s p roject. 18. 18. Conduction in different types of is a standalone [Type sidebar content. A sidebarmaterials cont… supplement to the main document. It is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab to change the formatting of the sidebar text box.] conduction band. If we take some water (electrons) from the valence band and move it to the conduction band, we will have place for the water (electrons) to move in both bands. If we tip our cup, water will move both in the valence and conduction band. Thus, in a semiconductor at room temperature, a small current will flow. In an insulator, the valence band is completely filled, and as a result no electrons can move. In the cup, no water will move no matter how we tip it. The band gap between the valence and the conduction band is huge. To move water (electrons) from our valence compartment to the conduction compartment, we would need to add such an amount of energy that our cup (material) would be close to breaking before any water (electrons) would begin to move between the compartments. 18 | p h y s i c s p r o j e c t . 19. 19. Doping … Doping..cont.. Now we are going to talk about doping. Maybe the word makes you think of athletes taking illegal drugs to perform better. Although doping in sports is outrageous, the parallel between that and doping of semiconductors is not too farfetched. In both cases you have something pure, like an athlete or a semiconducting material, and add something foreign to it to change its performance. So, in the process of doping you add a tiny amount of atoms from another material to the pure semiconductor. By doing so, you can drastically increase its ability to conduct a current. There are two forms of doping, p and n. p stands for positive and n for negative. Finally, two words that are good to know: a pure non-doped semiconductor is called intrinsic, while a doped semiconductor material is called extrinsic. 19 | p h y s i c s p r o j e c t . 20. 20. Pure semiconductors.. Before we look at examples of doped semiconductors, let's look at how the silicon atoms in pure silicon interact to form the crystal structure of the material. In pure silicon, each atom has four valence electrons and these are shared with four neighboring silicon atoms to make four double bonds. Now each atom will have a completely filled valence shell of eight electrons. At low temperature this bond is very stable, completely filling the valence band and thus making conduction impossible. Here is a model of the structure of pure silicon: In a pure 7 | p h y s i c sat plow roje ct. semiconductor temperature, the valence layer is completely filled with electrons and the conduction band is empty. That would be equal to one filled and one empty compartment in my http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

7/25

9/22/2015


cup. The water (electrons) can't move because there is no empty space. 20 | p h y s i c s p r o j e c t . 21. 21. P doping p-doping is when you add atoms with less valence electrons to the semiconductor so that the material gets a shortage of electrons in the crystal bonds. This way positive holes that can semiconductors..??? transportWhy current are formed. The materials that add holes are called acceptors because they accept electrons from the surrounding atoms. In a p-type semiconductor the major carrier of current are the holes, not the electrons. The p in p-doping stands for positive. This is because compared to the atoms in the semiconductor material the added atoms have fewer negative valence electrons. In the pdoped semiconductor the higher conduction band is empty, but there will be holes in the valence band. In the cup, this means that we remove some water from the valence compartment. In other words, we form air bubbles (positive holes) in the water. Now if we tip the cup, there is room for the water (electrons) to move in one direction and for the created holes (lack of electrons) to move in the opposite direction (just like bubbles would do in water). 21 | p h y s i c s p r o j e c t . 22. 22. N-doping… In the process of n-doping you add atoms with one extra valence electron to the pure semiconducting material. This creates a situation where there are extra electrons that are just loosely bound in the crystal. The amount of energy needed to get these electrons to jump to the conduction band so that a current may pass is very small. The materials that add electrons are called donors. This is simply because they donate electrons to the semiconductor. In the n-type semiconductor the major carrier of current is the negative electrons. The n in n-doping stands for negative. This is because compared to the atoms in the semiconductor material the added atoms have more negative valence electrons. In the ndoped semiconductor, the valence band is full so there is no room for the electrons to move there. Instead, the extra electrons move into the conduction band. In our cup, we can see that no water will move in the full valence compartment. Instead, the extra water (electrons) added will move within the conduction compartment. 22 | p h y sicsproject. 23. 23. Semiconductors-the future In a world where computers become faster and faster each year, semiconductor components, like chips and transistors, must be made smaller and smaller. This means that we will eventually reach a limit on how much faster and more effective the Silicon based technique can be made (in fact, devices operating with just a single electron have already been demonstrated). "What happens then?" you might ask yourself. Well we don't know for sure, but today's scientists are working hard to find new materials or to improve old ones. In the future, large molecules might do the work that transistors do today. This field is called Molecular Electronics. So hopefully (if you like information technology, that is) computers can continue to evolve for a long time to come. 23 | p h y s i c s p r o j e c t . 24. 24. Circuit diagram… Characteristics of transistor.. Transistor as amplifier. Transistor as switch 24 |physicsproject. 25. 25. Circuit diagrams.. Full wave rectifier. half wave rectifier. 25 | p h y s i c s p r o j e c t . 26. 26. Circuit diagram… logic gates… Integrated circuit 26 | p h y s i c s p r o j e c t . 27. 27. 27 | p h y s i c s p r o j e c t . Recommended More from this author 8 | p h y s i c s p r o j e c t .

Managing Project Risk

Semiconducting materials..!! http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

8/25

9/22/2015


Managing Project Schedules

Semiconductors can be made of a single material or a combination of several different materials. In early semiconductor devices germanium was often used. However in today's semiconductor industry, Rescuing Troubled Projects silicon is commonly used.

Silicon is very easy to find in Nature. Ordinary sand, like on the beach or in the desert for example, is nothing more than one silicon atom combined with two oxygen atoms. However, if you want silicon in its pure form suitable for the production of, for instance, Physics Investigatory Project Class 12 computer chips it has to be purified in a carefully monitored process. RAHUL 247,132

One of the main reasons for the popularity of silicon is that it is stable and can be heated to a rather high degree without loosing its material characteristics. This means that engineers can be sure it will perform according to their plans, even under quite extreme conditions.

Physics project class 12 EMI saisathvick 102,317 9 | p h y s i c s p r o j e c t .

[Type sidebar content. Semiconducting materials A sidebar cont….is a standalone supplement to the main document. It is often aligned on the left or right of the

20,000 Students have made physics projects from this list!! page, or located at the top or bottom. Use the Text Box Tools tab Gurpawan Mand 36,987 to change the formatting of the sidebar text box.] http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

9/25

9/22/2015


physics project sauravpandey17 41,216

Just to make sure we avoid misunderstandings, when we talk about silicon, we don't mean silicone spelled with an "e" at the end, 'cause that is a material mostly known for its use in human implants.

To understand the principles of semiconductors, it is CBSE Class XII physics practical project on Metal detector Pranav Ghildiyal good to first understand the basics of atoms and 24,283 energy levels within atoms. So that's where we're going to start.

Transformers Project report Tanuj Gupta 104,002

Physics project Sri Krishna 28,977


12th CBSE Physics Project AC Generator Ashwin Silicon Francis and its molecules.. 21,658

Physics Investigatory Project on Fluid Mechanics ashrant If we look at the solid material of Silicon we will see 18,190

that it is built from a huge number of Silicon atoms


10/25

9/22/2015


that brought When interact withare each other, together. the atomic shellsthe of atoms each atom interacts with the atomic shells of neighboring atoms. On an energy scale, the overlapping energy shells of all the separate atoms form energy bands that are Physics investigatory project similar to the energy shells in the single atom. mihika13 Between the bands no electrons are allowed. In a 43,059 simplified way, it is almost as if the solid material is an enlargement of the single atom.

Semiconductor physics speaking technology 10,118

Optical fibers physics project menna94 10,105


Physics project Jayashree Venkatesh 7,223

Bands and their theories...

Chemistry Investigatory Project Class 12 RAHUL 125,087

To continue our journey, you don't need to fully understand what Sally just said. But what you do need to understand is, that the Semiconductor Devices Classenergy 12 Part-1band that is occupied by highest RAHUL electrons in a material is called the valence 5,746 band, just like in the single atom where the http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

11/25

9/22/2015


highest shell occupied by electrons is called the valence shell. The band with energy one step higher than the valence band is theconduction band. The energy gap between these two bands, where no electrons are allowed, is called the band . Foootbal physicalgap education Aashirwad Jindal 10,554

If you think of the energy bands as steps in a staircase then the band gap is the area between the steps. You can put your foot on the first step of the stairs and you can put it on the second, but you can never put it mettalurgy-12th sci cbse Aashirwad Jindal 12 | p h y s i c s p r o j e c t . 442 ENGLISH English Français Español Português (Brasil) Bands and their theories... cont… Deutsch English Espanol Portugues Français Deutsche

somewhere between the first and second.

About Dev & API Blog Terms Privacy Copyright Support


12/25

9/22/2015


LinkedIn Corporation © 2015 × Share Clipboard

× Email

Enter email addresses Add a message

From Send

Email sent successfully.. 13 | p h y s i c s p r o j e c t .

Facebook Twitter LinkedIn Google+ Link

A electron-hole pair..!! Public clipboards featuring this slide

×

A very important feature of the semiconductor material is the electron-hole pair. To get a semiconductor to conduct a current, we must make an electron jump from an occupied to an unoccupied energy level. When it does this it leaves a hole (an empty state). This hole can be filled by another electron, which itself leaves a new hole. Therefore, we could say that both the hole and the No public clipboards found for thiscontribute slide electron to the conductivity as they move around in the material. The hole is like a positive charge (lack of negative), the electron is negative.


13/25

9/22/2015


It's a little bit like this simple puzzle game where you move pieces around to form an image. The moving pieces correspond to the electrons, of course.


Conduction in different types of materials…

As mentioned earlier, the semiconductor has a conducting capacity somewhere between the conductor and the insulator. If we look closer at the materials we can see why they behave like this. Before we go on, note that contrary to what its name may suggest, the conduction band is not the only band where conduction of a current may occur. Conduction is equally possible in the valence band.


14/25

9/22/2015


In a good conductor like a metal, the highest energy band with electrons (valence band) is only partially filled. This means that the electrons can accelerate. In other words, they gain energy so that they can transfer to


Conduction in different different types of materials…

higher energy levels that are empty. Simply put, in a conductor there is plenty of room for the electrons to jump from an occupied state to an empty one.

If you felt that Sally's explanation of the conduction properties in different materials was crystal clear, you can skip the following part. But if you're still a little unsure of how it works, I will try to show you another way of looking at this phenomenon. To help my explanation, I am going to use the unrealistic cup with the water-filled compartments again. The compartments e ual the ener bands of the material and the water http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

15/25

9/22/2015



Conduction in different types of materials…

equals the electrons. This time the cup only has two compartments, one for the valence band and one for the conduction band.

In a conductor, the valence band is only partially filled. This means that, in our cup, we are going to have the valence compartment half -filled with water. If we tip the cup from side to side, we will see that it is easy for the water to move back and forth, just as it is easy for the electrons to move within the conductor.

A semiconductor at low temperature is an insulator because there is no place for the electrons to go to. The valence compartment is filled and no matter how we tip the cup there is no room for the water to move into. At room temperature, the heat (energy) makes the atoms vibrate slightly, enough for a few of the electrons to break their bonds and jump into the 17 | p h y s i c s p r o j e c t .


16/25

9/22/2015


Conduction [Type sidebar in content. differentAtypes sidebar of materials is a standalone cont… supplement to the main document. It is often aligned on the left or right of the page, or located at the top or bottom. Use the Text Box Tools tab to change the formatting of the sidebar text box.] conduction band. If we take some water (electrons) from the valence band and move it to the conduction band, we will have place for the water (electrons) to move in both bands. If we tip our cup, water will move both in the valence and conduction band. Thus, in a semiconductor at room temperature, a small current will flow.

In an insulator, the valence band is completely filled, and as a result no electrons can move. In the cup, no water will move no matter how we tip it. The band gap between the valence and the conduction band is huge. To move water (electrons) from our valence compartment to the conduction compartment, we would need to add such an amount of energy that our cup (material) would be close to breaking before any water (electrons) would begin to move between the compartments.


Doping … Doping..cont.. http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

17/25

9/22/2015


Now we are going to talk about doping. Maybe the word makes you think of athletes taking illegal drugs to perform better. Although doping in sports is outrageous, the parallel between that and doping of semiconductors is not too far fetched. In both cases you have something pure, like an athlete or a semiconducting material, and add something foreign to it to change its performance.

So, in the process of doping you add a tiny amount of atoms from another material to the pure semiconductor. By doing so, you can drastically increase its ability to conduct a current. There are two forms of doping, p and n. p stands for positive and n for negative. Finally, two words that are good to know: a pure non-doped semiconductor is called intrinsic, while a doped semiconductor material is called extrinsic.


Pure semiconductors..


18/25

9/22/2015


Before we look at examples of doped semiconductors, let's look at how the silicon atoms in pure silicon interact to form the crystal structure of the material. In pure silicon, each atom has four valence electrons and these are shared with four neighboring silicon atoms to make four double bonds. Now each atom will have a completely filled valence shell of eight electrons. At low temperature this bond is very stable, completely filling the valence band and thus making conduction impossible. Here is a model of the structure of pure silicon:

In a pure semiconductor at low temperature, the valence layer is completely filled with electrons and the conduction band is empty. That would be equal to one filled and one empty compartment in my cup. The water (electrons) can't move because there is no empty space. 20 | p h y s i c s p r o j e c t .

P doping

p-doping is when you add atoms with less valence electrons to the semiconductor so that the material gets a shortage of electrons in the crystal bonds. This way positive holes that can transport current are formed. The materials that add holes are http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

19/25

9/22/2015


called acceptors because they accept electrons from the surrounding atoms. In a p -type semiconductor the major carrier of current are the holes, not the electrons.

The p in p -doping stands for positive. This is because compared to the atoms in the semiconductor material the added atoms have fewer negative valence electrons. In the p doped semiconductor the higher conduction band is empty, but there will be holes in the valence band. In the cup, this means that we remove some water from the valence compartment. In other words, we form air bubbles (positive holes) in the water. Now if we tip the cup, there is room for the water (electrons) to move in one direction and for the created holes (lack of electrons) to move in the opposite direction (just like bubbles would do in water). 21 | p h y s i c s p r o j e c t .

N-doping…

In the process of n -doping you add atoms with one extra valence electron to the pure semiconducting material. This creates a situation where there are extra electrons that are just loosely bound in the crystal. The amount of energy needed to get these electrons to jump to the conduction band so that a current may pass is very small. The materials that add electrons are called donors. This is simply because they donate electrons to the semiconductor. In the n -type semiconductor the major carrier of current is the negative electrons. http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

20/25

9/22/2015


The n in n -doping stands for negative. This is because compared to the atoms in the semiconductor material the added atoms have more negative valence electrons. In the n doped semiconductor, the valence band is full so there is no room for the electrons to move there. Instead, the extra electrons move into the conduction band. In our cup, we can see that no water will move in the full valence compartment. Instead, the extra water (electrons) added will move within the conduction compartment.


Semiconductors-the future

In a world where computers become faster and faster each year, semiconductor components, like chips and transistors, must be made smaller and smaller. This means that we will eventually reach a limit on how much faster and more effective the Silicon based technique can be made (in fact, devices operating with just a single electron have already been demonstrated). "What happens then?" you might ask yourself. Well we don't know for sure, but today's scientists are working hard to find new materials or to improve old ones. In the future, large molecules might do the work that transistors do http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

21/25

9/22/2015


. . hopefully (if you like information technology, that is) computers can continue to evolve for a long time to come.


Circuit diagram… Characteristics of transistor..

Transistor as amplifier.

Transistor as switch http://www.slideshare.net/AashirwadJindal/physics-semiconductors-project

22/25

9/22/2015



Circuit diagrams.. Full wave rectifier.

half wave rectifier.


23/25

9/22/2015



Circuit diagram…

logic gates… Integrated circuit


24/25

9/22/2015





25/25

Physics Semiconductors Project

Recommend Documents