Lecture 1 Introduction to Semiconductor Physics_Fall 2023.pdf

Lecture Slides for Electronic Engineering

1. Electronic
Engineering
EE-2006

2. Course Details
Introduction to Semi-conductor Physics
PN Junction and its Characteristics
Diode
Rectifiers & Power Supply
Clippers and Clampers
Zener Diodes
BJTs and their Structure
VI Characteristics of BJTs
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3. Course Details
BJT Circuits at DC-DC Analysis
Amplifiers using BJTs (Single and Multistage)
MOSFETs
Operational Amplifiers (Op Amps)
Applications of Op-Amps
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4. Course Material
Text Book:
Electronic Devices by Thomas L. Floyd 9
th
edition
Reference Book:
Microelectronic Circuits by SedraSmith 7
th
edition
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5. Introduction to Semiconductor
Physics
Structure of an Atom
Materials used in electronics
Conductors, insulators and semiconductors
Silicon and Germanium
Concept of electrons and holes
N-type and P-type semiconductors
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6. Structure of an Atom
An atom consists of
An electron
A proton
A neutron
An electrically balanced (neutral)
atom has equal no. of electrons &
protons
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7. Energy Levels
Electrons orbit around the nucleus at some distance
from the nucleus.
Discrete distance from the nucleus is known as orbit.
Each orbit corresponds to a certain energy level
also known as ‘shells’.
Each atom has fixed no. of shells and each shell has
fixed no. of electrons.
Maximum no. of electrons in a shell is 2??????
2
,where ??????is
no. of shells.
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8. Materials used in Electronics
Conductor
A conductor is an element which conducts heat or
electricity
Insulator
An insulator is an element which does not conduct
heat or electricity
Semiconductors
Semiconductors are elements whose properties lie
between conductor and insulators. They are usually
group-IV elements. They have ability to conduct
electricity under certain circumstances.
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9. •Band Gap
The difference in energy between valence band and conduction
band is known as band gap. It is the amount of energy an electron
must possess in order to jump from valence band to conduction
band.
•For conductors, there are always free electrons in conduction band,
there is no band gap
•For insulators, there is a wide band gap
•For semi-conductors, the band gap is small.
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10. Band Gap for Conductors,
Insulators and Semi-conductors
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11. Materials used in Electronics
Silicon (Si)
Four valence electrons in 3
rd
shell (atomic no.:14)
Has lower energy in valence electrons
More stable
Used in diodes, transistors, ICs etc.
Germanium (Ge)
Four valence electrons in 4
th
shell (atomic no.: 32)
Has more energy in valence electrons
Unstable as compared to Si
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12. Concept of Electrons & Holes
An intrinsic Si crystal has sufficient energy at room
temperature for valence electrons to jump from
valence band into conduction band. These free
electrons are called ‘conduction electrons’
The vacancy left in valence band is represented by
a ‘hole’ creating an ‘electron-hole’ pair
The falling back of electron from conduction band
to valence band into the hole is known as
‘Recombination’
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13. Electron Current & Hole
Current
When voltage is applied
to Si crystal, free electrons
are attracted towards
positive end causing
current to flow known as
‘electron current.’
Similarly movement of
holes is known as ‘hole current’
also called conventional current.
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14. Types of Semiconductors
Semi-conductors do not conduct electricity in
normal state, we need to add impurities (doping) to
make current flow through them
With respect to doping, there are two types of semi-
conductors:
N-type
P-type
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15. Types of Semiconductors
N-type Semiconductors
Pentavalentimpurities are added such as Arsenic(As),
Phosphorus(P), Antimony(Sb) and Bismuth(Bi)
Have majority electrons as carriers
Have holes as minority carriers
P-type Semiconductors
Trivalent impurities are added such as Boron (B), Indium
(In)and Gallium (Ga)
Have majority holes as carriers
Have electrons as minority carriers
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16. Types of Semiconductors
N-Type P-Type
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17. Thank You.
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