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Transcript of Electronics Principles & Applications Fifth Edition Chapter 2 Semiconductors ©1999...
![Page 1: Electronics Principles & Applications Fifth Edition Chapter 2 Semiconductors ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader035.fdocuments.in/reader035/viewer/2022062305/5697bff11a28abf838cbb091/html5/thumbnails/1.jpg)
ElectronicsElectronics
Principles & ApplicationsPrinciples & ApplicationsFifth EditionFifth Edition
Chapter 2Semiconductors
©1999 Glencoe/McGraw-Hill
Charles A. Schuler
![Page 2: Electronics Principles & Applications Fifth Edition Chapter 2 Semiconductors ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader035.fdocuments.in/reader035/viewer/2022062305/5697bff11a28abf838cbb091/html5/thumbnails/2.jpg)
• Conductors and Insulators• Semiconductors• N-type Semiconductors• P-type Semiconductors• Majority and Minority Carriers
INTRODUCTION
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NN
NN
The center of an atom is called the nucleus.Most atoms have neutrons which have no charge.A nucleus also has protonsand they have a positive charge.
Negative electronsorbit the nucleus.
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NN
NN
This is a copper atom.
It has 29 protons.
It has 29 electrons.
Its net charge = 0.
Valence electron
![Page 5: Electronics Principles & Applications Fifth Edition Chapter 2 Semiconductors ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader035.fdocuments.in/reader035/viewer/2022062305/5697bff11a28abf838cbb091/html5/thumbnails/5.jpg)
The valence electron is the important feature.
NN
NN
Valence electron
Its attraction to the nucleus is relatively weak.
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The valence electron
The nucleus plus the inner electron orbits
A simple model of the copper atom looks like this:
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Copper wire is usedto conduct electricitybecause the valence
electrons move freelythrough its structure.
Remember, the valenceelectrons are weakly
attracted to the nuclei.
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So far, we know that copper’s single valence electron makes it a good conductor.
It acts as an electrical insulator.
The rule of eight states that a material like thiswould be stable since its valence orbit is full.
No Vacancy
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Atomic quiz
The dense and central part of any atom iscalled the ________. nucleus
Atom net charge is 0 since the number of protonsequals the number of ______. electrons
The outermost orbit of all atoms is calledthe ________ orbit. valence
Good electrical conductors have freevalence ________. electrons
The magic number for valence stabilityis ________. eight
![Page 10: Electronics Principles & Applications Fifth Edition Chapter 2 Semiconductors ©1999 Glencoe/McGraw-Hill Charles A. Schuler.](https://reader035.fdocuments.in/reader035/viewer/2022062305/5697bff11a28abf838cbb091/html5/thumbnails/10.jpg)
Atoms of the same type can join together and form covalent bonds.
This is an electron sharing process.
Silicon atoms have four valence electrons.
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The covalent sharing satisfies the rule of eight.
In this structure, one bond is formed with each neighbor
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This is a silicon crystal.
It does not conduct because its valence electrons are held by covalent bonds.
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Thermal carriers
Covalent bonds can be broken by heating a silicon crystal.
Free electron
Hole
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The thermal carriers support the flow of current.
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Heating silicon crystals to make them conduct is not practical!
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This is an arsenic atom.
A silicon crystal can be doped with a donor impurity.
1
2 3
45
Each donor atom that enters the crystal adds a free electron.
Free electron
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Silicon that has been doped with arsenic is called N-type.
The free electrons in N-type silicon support the flow of current.
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This is a boron atom.
A silicon crystal can be doped with an acceptor impurity.
1
2 3Each acceptor atom that enters the crystal creates a hole.
Hole
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Silicon that has been doped with boron is called P-type.
The holes in P-type silicon support the flow of current.
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What are two practical methodsof making silicon semiconduct?
HoleFree electron
Add a pentavalentimpurity
Add a trivalentimpurity
(N type) (P type)
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This is a P-type crystal.
Due to heat, it could have a few free electrons.
These are called minority carriers.
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This is an N-type crystal.
Due to heat, it could have a few free holes.
These are called minority carriers.
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Semiconductor quiz
A pure silicon crystal, at room temperature,acts as an electrical ________. insulator
The current carriers, in N-type silicon, arecalled ________. electrons
The current carriers, in P-type silicon, arecalled ________. holes
The minority carriers, in N-type silicon, arecalled ________. holes
The minority carriers, in P-type silicon, arecalled ________. electrons
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REVIEW
• Conductors and Insulators• Semiconductors• N-type Semiconductors• P-type Semiconductors• Majority and Minority Carriers