Chapter 1 Semiconductors: A General Introduction
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Transcript Chapter 1 Semiconductors: A General Introduction
Semiconductor Device Physics
Lecture 1
Dr.-Ing. Erwin Sitompul
President University
http://zitompul.wordpress.com
President University
Erwin Sitompul
SDP 1/1
Semiconductor Device Physics
Textbook and Syllabus
Textbook:
“Semiconductor Device Fundamentals”,
Robert F. Pierret, International Edition,
Addison Wesley, 1996.
Syllabus:
Chapter 1: Semiconductors: A General Introduction
Chapter 2: Carrier Modeling
Chapter 3: Carrier Action
Chapter 5: pn Junction Electrostatics
Chapter 6: pn Junction Diode: I–V Characteristics
Chapter 7: pn Junction Diode: Small-Signal Admittance
Chapter 8: pn Junction Diode: Transient Response
Chapter 14: MS Contacts and Schottky Diodes
Chapter 9: Optoelectronic Diodes
Chapter 10: BJT Fundamentals
Chapter 11: BJT Static Characteristics
Chapter 12: BJT Dynamic Response Modeling
President University
Erwin Sitompul
SDP 1/2
Semiconductor Device Physics
Grade Policy
Grade Policy:
Final Grade = 10% Homework + 20% Quizzes +
30% Midterm Exam + 40% Final Exam +
Extra Points
Homeworks will be given in fairly regular basis. The average
of homework grades contributes 10% of final grade.
Homeworks are to be written on A4 papers, otherwise they
will not be graded.
Homeworks must be submitted on time. If you submit late,
< 10 min.
No penalty
10 – 60 min. –20 points
> 60 min.
–40 points
There will be 3 quizzes. Only the best 2 will be counted.
The average of quiz grades contributes 20% of final grade.
President University
Erwin Sitompul
SDP 1/3
Semiconductor Device Physics
Grade Policy
• Heading of Homework Papers (Required)
Grade Policy:
Midterm and final exam schedule will be announced in time.
Make up of quizzes and exams will be held one week after
the schedule of the respective quizzes and exams.
The score of a make up quiz or exam can be multiplied by 0.9
(the maximum score for a make up is 90).
President University
Erwin Sitompul
SDP 1/4
Semiconductor Device Physics
Grade Policy
Grade Policy:
Extra points will be given every time you solve a problem in
front of the class. You will earn 1 or 2 points.
Lecture slides can be copied during class session. It also will
be available on internet around 3 days after class. Please
check the course homepage regularly.
http://zitompul.wordpress.com
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Erwin Sitompul
SDP 1/5
Chapter 1
Semiconductors: A General Introduction
What is a Semiconductor?
Low resistivity
“conductor”
High resistivity
“insulator”
Intermediate resistivity “semiconductor”
The conductivity (and at the same time the resistivity) of
semiconductors lie between that of conductors and insulators.
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Erwin Sitompul
SDP 1/6
Chapter 1
Semiconductors: A General Introduction
What is a Semiconductor?
Semiconductors are some of the purest solid materials in
existence, because any trace of impurity atoms called “dopants”
can change the electrical properties of semiconductors
drastically.
Unintentional impurity level:
1 impurity atom per 109 semiconductor atom.
Intentional impurity ranging from 1 per 108 to 1 per 103.
No recognizable
long-range order
Entire solid is made up of
atoms in an orderly
three- dimensional array
Completely ordered
in segments
polycrystalline amorphous crystalline
Most devices fabricated today employ crystalline
semiconductors.
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Erwin Sitompul
SDP 1/7
Chapter 1
Semiconductors: A General Introduction
Semiconductor Materials
Elemental:
Si, Ge, C
Compound:
IV-IV
III-V
II-VI
Alloy:
Si1-xGex
AlxGa1-xAs
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SiC
GaAs, GaN
CdSe
Erwin Sitompul
SDP 1/8
Chapter 1
Semiconductors: A General Introduction
From Hydrogen to Silicon
# of Electrons
1
2
3
Z Name 1s 2s 2p 3s 3p 3d
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Notation
1
1H
1
1s
2 He
2
1s 2
3 Li
2
1
1s 2 2s 1
4 Be
2
2
1s 2 2s 2
5B
2
2
1
1s 2 2s 2 2p1
6C
2
2
2
1s 2 2s 2 2p2
7N
2
2
3
1s 2 2s 2 2p3
8O
2
2
4
1s 2 2s 2 2p4
9F
2
2
5
1s 2 2s 2 2p5
10 Ne
2
2
6
1s 2 2s 2 2p6
11 Na
2
2
6
1
1s 2 2s 2 2p6 3s 1
12 Mg
2
2
6
2
1s 2 2s 2 2p6 3s 2
13 Al
2
2
6
2
1
1s 2 2s 2 2p6 3s 2 3p1
14 Si
2
2
6
2
2
1s 2 2s 2 2p6 3s 2 3p2
15 P
2
2
6
2
3
1s 2 2s 2 2p6 3s 2 3p3
16 S
2
2
6
2
4
1s 2 2s 2 2p6 3s 2 3p4
17 Cl
2
2
6
2
5
1s 2 2s 2 2p6 3s 2 3p5
18 Ar
2
2
6
2
6
1s 2 2s 2 2p6 3s 2 3p6
Erwin Sitompul
SDP 1/9
Chapter 1
Semiconductors: A General Introduction
The Silicon Atom
14 electrons occupying the first 3 energy levels:
1s, 2s, 2p orbitals are filled by 10 electrons.
3s, 3p orbitals filled by 4 electrons.
To minimize the overall energy, the 3s and
3p orbitals hybridize to form four
tetrahedral 3sp orbital.
Each has one electron and is capable of
forming a bond with a neighboring atom.
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Erwin Sitompul
SDP 1/10
Chapter 1
Semiconductors: A General Introduction
The Si Crystal
• Each Si atom has 4 nearest
neighbors.
• Atom lattice constant
(length of the unit cell side)
° 1A=10
°
–10m
a = 5.431A,
• Each cell contains:
8 corner atoms
6 face atoms
4 interior atoms
a
“Diamond Lattice”
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Erwin Sitompul
SDP 1/11
Chapter 1
Semiconductors: A General Introduction
How Many Silicon Atoms per cm–3?
Number of atoms in a unit cell:
4 atoms completely inside cell
Each of the 8 atoms on corners are shared among 8 cells
count as 1 atom inside cell
Each of the 6 atoms on the faces are shared among 2 cells
count as 3 atoms inside cell
Total number inside the cell = 4 + 1 + 3 = 8
Cell volume = (.543 nm)3 = 1.6 x 10–22 cm3
Density of silicon atom
= (8 atoms) / (cell volume)
= 5 x 1022 atoms/cm3
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SDP 1/12
Chapter 1
Semiconductors: A General Introduction
Compound Semiconductors
“Zincblende” structure
III-V compound semiconductors: GaAs, GaP, GaN, etc.
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SDP 1/13
Chapter 1
Semiconductors: A General Introduction
Crystallographic Notation
Miller Indices
Notation
Interpretation
(hkl)
crystal plane
{hkl}
equivalent planes
[hkl]
crystal direction
<hkl>
equivalent directions
h: inverse x-intercept of plane
k: inverse y-intercept of plane
l: inverse z-intercept of plane
(h, k and l are reduced to 3
integers having the same ratio.)
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SDP 1/14
Chapter 1
Semiconductors: A General Introduction
Crystallographic Planes
(632) plane
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(001) plane
Erwin Sitompul
_
(221) plane
SDP 1/15
Chapter 1
Semiconductors: A General Introduction
Crystallographic Planes
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Chapter 1
Semiconductors: A General Introduction
Crystallographic Planes of Si Wafers
Silicon wafers are usually cut along a {100} plane with a flat or
notch to orient the wafer during integrated-circuit fabrication.
The facing surface is polished and etched yielding mirror-like
finish.
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Erwin Sitompul
SDP 1/17
Chapter 1
Semiconductors: A General Introduction
Crystal Growth Until Device Fabrication
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SDP 1/18
Chapter 1
Semiconductors: A General Introduction
Crystallographic Planes of Si
Unit cell:
View in <111> direction
View in <100> direction
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View in <110> direction
Erwin Sitompul
SDP 1/19
Chapter 1
Semiconductors: A General Introduction
Greek Alphabet
—new
—zz-eye
—pie
—taw
—fie
—k-eye
—sigh
—mew
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Erwin Sitompul
SDP 1/20