EE 3323
Electronic Devices
Prof. Youngjoong Joo
University of Texas at San Antonio
INSTRUCTOR
Dr. Youngjoong Joo
Dept. of Electrical Engineering
The University of Texas at San Antonio
One UTSA Circle
San Antonio, Tx 78249
Office: AET 2.362
Telephone: (210) 458-6098
E-Mail: youngjoong.joo@utsa.edu
Web Site:
Office Hours: Wednesday (1:00pm - 2:30pm)
COURSE INFORMATION
Homework: Homework should be done neatly and is due at lecture time.
You will lose points if the homework is messy. Late Homework will not
be accepted.
Computers: Use of software (e.g., MathCad, Matlab, Mathematica,
Spreadsheet, TK Solver, etc.) to solve some homework problems is
recommended for two reasons: it makes life easier for you and if you do
not know such programs it forces you to learn them.
Textbook:
R.F. Pierret, Semiconductor Device Fundamentals, Addison-Wesley, 1996.
Exams:
Feb. 11, Mar. 25, 2010. Final May 5, 2010, 10:30 am.
All exams must be taken as scheduled.
Final Grade: Intermediate Exams:
Final Exam:
Homework:
50%
25%
25%
Welcome
Welcome to 3323 Elctronic Devices.
This is a most useful course if
You are planning to work in the field of semiconductors
You want to get an overview of how semiconductor devices
function
It will give you a good overview of
Semiconductor materials
Basic material properties
The prerequisite for this course is a course in properties of
electronic materials, e.g., UTSA’s CHE 1103 and EE3213
You should be familiar with basic physics of solids, band
diagrams, crystal bonds, wave equation, very basic
semiconductors
Objectives
Understand the operation of the basic semiconductor
devices
Understand device physics (energy bands, carrier
statistics, recombination, and carrier drift and diffusion)
After discussing these aspects of semiconductors, we
will concentrate on:
pn junctions
Metal-semiconductor devices
Metal-oxide semiconductor capacitors and transistors
Bipolar junction transistors
Emphasis will be on the conceptual understanding of device
operation rather than on memorization of equations
Your Responsibility
It is your responsibility to master the material
I will assign homework so that you have to
apply the course material and reinforce learning
Remember we typically retain only about
20% of what we hear
30% of what we see
Up to 90% by participating in discussions or other
active experience
The textbook is supplementary material that
you should consult
Course Outline
Fundamentals
Introduction
Impact and Use of
Semiconductors
What is a Semiconductor
Semiconductor Materials
Crystal Structure
Wafer Orientation
Bonds and Bands
Carrier Densities
Current Flow
Recombination/Generation
Continuity Equation
PN Junctions
Introduction
Fabrication
Statics
Ideal Current-Voltage
Breakdown
R-G Current
Capacitance
Transients
Applications
Course Outline
Metal-Semiconductor Devices
Introduction
Metal-Semiconductor
Junction
Schottky Diode
Ohmic Contact
Applications
Field-Effect Devices
Introduction
MOS Capacitor - Basics
MOS Capacitor - Quantitative
MOS Capacitor - C-V
MOSFET - Qualitative
MOSFET - Quantitative
MOSFET - Nonidealities
Complementary MOS
Applications
Bipolar Junction
Transistors
Introduction
Fabrication
Minority Carriers
Currents
Gain
Current Crowding
Nonidealities
Applications
Appendices
FUNDAMENTALS
Density of States
Diamond Lattice
Direct/Indirect Band Gap
Semiconductors
Effective Mass
Electron-Volt
Energy Levels
Equilibrium
Fermi Function
Fermi Integral
Intrinsic Carrier Density
Light
Miller Indices
Mobility
Pauli Exclusion Principle
Periodic Table
Phonons
Photons
Powers of Ten
Quasi-Fermi Level
Sloped Energy Band
Units
PN JUNCTIONS
Avalanche Breakdown
Built-in Potential
Continuity Equation
Excess Carriers
Poisson’s Equation
Tunnel Breakdown
Appendices
METAL-SEMICONDUCTOR
DEVICES
Ohmic Contacts
Schottky Diodes
Work Function
MOS DEVICES
Drain Conductance,
Transconductance
Load Lines
Mobility
MOSFET Symbols
Oxide Charges
Threshold Voltage
BIPOLAR JUNCTION
TRANSISTORS
Base Transport Factor
Base Width Modulation
BJT Symbols
Ebers-Moll Equations
Emitter Efficiency
Junction Breakdown
Leakage Current
Punchthrough
Suggested Course Schedule
Week 1
Introduction, Semiconductors,
MOS Capacitor, Band Diagrams,
Miller Indices, Growth, Bonds
Week 2
Threshold Voltage
Carrier Statistics
Week 3
Week 4
Week 5
Voltage, Nonidealities
Transistor, Minority Carriers
PN Junctions: Current-Voltage,
Breakdown
Week 7
PN Junctions: Switching,
Schottky Diodes, MOS Band
Diagrams
Week 12
CMOS, Bipolar Junction
Potential
Week 6
Week 11
MOSFET: Advanced Current-
PN Junctions: Electric Field,
Week 10
MOSFET: Current-Voltage
Continuity Equations
Week 9
MOS-C: Capacitance, MOSFET
Energy, Potential, Drift,
Diffusion, Recombination
Week 8
Week 13
BJT: Current-Voltage
Week 14
BJT: Ebers-Moll, Gain
Week 15
BJT: Breakdown, Crowding
Say The Color, Not The Word
Course Outline
Semiconductor Fundamentals
PN Junctions
Metal-Semiconductor Junctions
Field Effect Devices
Bipolar Junction Transistors
The Ideal
Should
Take no space
Weigh nothing
Use no power
Cost nothing
Require no maintenance
Require no training to operate
Last forever
Semiconductor devices come close!
Semiconductor Fundamentals
Crystals
Some Background
What is a Semiconductor
Crystal Growth, Crystal Structure
Wafer Orientation, Miller Indices
Energy Levels, Bonds and Bands
Energy Levels
Bonds and Bands
Carriers
Carrier Statistics
Drift/Diffusion
Recombination, Generation
Continuity Equation
Semiconductor Fundamentals
Crystals
Some Background
What is a Semiconductor
Crystal Growth, Crystal Structure
Wafer Orientation, Miller Indices
50 Years Progress
John Bardeen
Walter Brattain
William Shockley
Bell Laboratory - 1947
1 Transistor
Motorola PC 620 - 1997
7,000,000 Transistors
First Integrated Circuits
Robert Noyce
Jack Kilby
Fairchild
Texas
Instruments
First IC at Fairchild
Semiconductor, 1958
First IC at Texas Instruments
1958
Si Valley History
108
Encyclopedia
102
64 M
Book
106
104
DRAM
16 G
1G
4M
Double
/1.5 Yrs
256 K
Page 16 K
Double/2 Yrs
1K
Product
SIA Roadmap
Double/1 Yr
100
1960 1970 1980 1990 2000 2010
Dimension (µm)
1010
10
10
Gate Length
1
0.1
Junction
Depth
0.01
0.001
1970
Year
1
Oxide Thickness
1980
1990
2000
0.1
2010
Chip Area (cm2)
Transistors/Chip
Information Storage Capacity of ICs
Year
How a model 1970 automobile would perform, had it improved at the
same rate as integrated circuits
Speed (mph)
Power (mpg)
Cost (1992 $)
Mass (kg)
Luggage (ft3)
1970
1995
100
20
20,000
1,500
20
2,500,000
1,740,000
40
0.06
80,000
Worldwide Semiconductor Sales
Billion Dollars
300
250
200
150
100
50
0
1970
1980
1990
Year
2000
Money Accumulation
When you retire you will need about $ 2 million in your
retirement account to live comfortably
If you deposit $ 2000 into
an account and add $ 2000
each year at various
interest rates, you will have:
Million $
It is important to start
early in your career!
4
14%
3
2
12%
1
10%
8%
0
0
10
20
Years
30
40
Units
The semiconductor world uses a mixture of units
Device dimensions usually given in microns (micrometers)
Oxide thickness is given in angstroms (Å) or nanometers (nm)
Wafer diameters are given in millimeters (mm) or inches (200
mm wafer is often also called eight inches)
Sometimes mils are used for wafer thickness or chip size
1 Å (angstrom) = 10-8 cm = 10-10 m
1 nm (nanometer) = 10-7 cm = 10-9 m
1 µm (micron) = 10-4 cm = 10-6 m
1 mil = 10-3 inches = 25.4 µm
Powers Of Ten
1024
yotta
Y
10-1
deci
d
1021
zetta
Z
10-2
centi
c
1018
exa
E
10-3
milli
m
1015
peta
P
10-6
micro
µ
1012
tera
T
10-9
nano
n
109
giga
G
10-12 pico
p
106
mega
M
10-15 femto
f
103
kilo
k
10-18 atto
a
102
hecto
h
10-21 zepto
z
101
deka
da
10-24 yocto
y
Semiconductor Fundamentals
Crystals
Some Background
What is a Semiconductor
Crystal Growth, Crystal Structure
Wafer Orientation, Miller Indices
What Is A Semiconductor?
A semiconductor has a “so-so” conductivity; it neither as
conductive as a metal nor as resistive as an insulator
Its conductivity is varied during crystal growth by incorporating
dopant atoms into the melt and during device fabrication by
adding dopant atoms to various regions of the device
The conductivity, σ, is given by
σ = q (nµ n + pµ p )
q is the charge of an electron (1.6x10-19 C), n and p are the electron and hole
densities (cm-3) and µn and µp are the electron and hole mobilities (cm2/V-s)
The resistivity, ρ, is given by
ρ=
1
σ
Resistivity
The resistivity of materials varies over a wider range
than any other property of materials
It is difficult to vary the resistivity of a metal or of an
insulator
It is easy to vary the resistivity of a semiconductor
Si: 10-3 ≤ ρ ≤ 104; GaAs: 10-3 ≤ ρ ≤ 108 ohm-cm
Metals
Semiconductors
10-6 10-4 10-2 100
10-2 104
106
Insulators
108
Resistivity (ohm-cm)
1010 1012 1014
Resistivity
Semiconductor resistivity depends on carrier density
and mobility
ρ=
Resistivity (ohm톍m)
1
q (nµ n + pµ p )
104
Boron
102
Silicon
100
Phosphorus
10-2
10-4
1012
1014
1016
1018
Dopant Density
1020
(cm-3)
Semiconductors
Semiconductors come in various types, i.e., elemental
(group IV: Si, Ge, etc.) or compound (group III-V: GaAs,
InP, group II-VI: ZnSe, CdS, etc.)
The various types can be found in the Periodic Table
II
III
IV
V
VI
Be
Mg
Zn
Cd
Hg
B
Al
Ga
In
Tl
C
Si
Ge
Sn
Pb
N
P
As
Sb
Bi
O
S
Se
Te
Po
Group IV
Group III-V
Group II-VI
Semiconductors
Group IV
Silicon is the most common, used for most of the
integrated circuits and power devices; SiC for hightemperature devices
Group III-V
GaAs is the most common, used for light emitting
devices and high-speed devices/circuits; GaN, GaAsP
for light emitters, GaInAsP for optical communication
systems
Group II-VI
ZnO: lightning arresters, HgCdTe: infrared detectors
Review Questions
What material parameters determine the
semiconductor resistivity?
Which one material parameter influences the
semiconductor resistivity the most?
What does “group IV” etc. mean?
Which groups form semiconductors, i.e.,
groups II to VI?
Semiconductor Fundamentals
Crystals
Some Background
What is a Semiconductor
Crystal Growth, Crystal Structure
Wafer Orientation, Miller Indices
Czochralski Crystal Growth
Bring single
crystal seed
into the melt
Seed
Looks hot!
Molten Si (1414oC)
Dip seed into
melt and
withdraw
slowly
Seed is
necked
down
Polycrystalline
Silicon
Pull seed with
proper pull
rate and
rotation
Ingot
http://www.msil.ab.psiweb.com/english/msilhist0-e.html
Czochralski Crystal Growth
Seed
Single Crystal Si
Quartz Crucible
Water Cooled Chamber
Heat Shield
Carbon Heater
Graphite Crucible
Crucible Support
Spill Tray
Electrode
104
10
103
125
102
75
100
101
300 mm
200
150
50
1970
1980
1
1990
2000
0.1
2010
Chip Area (cm2)
Wafer Area (cm2)
Chip and Wafer Areas
Year
300 mm ingots, courtesy
of B. Kellerman, MEMC
Silicon Ingot / Wafers
300 mm
200 mm
Photos Courtesy of Wacker Siltronic
400 mm
Crystal Structure
Solids come in three versions: amorphous,
polycrystalline, and single crystal
Amorphous: no long-range order (e.g., glass)
Polycrystalline: single-crystal grains separated by grain
boundaries (e.g., most metals)
Single crystal: the entire solid is one single crystal material
(e.g., silicon wafer)
Single
Crystal Grain
Amorphous
Grain Boundary
Polycrystalline
Single Crystal
Crystal Structure
Tetrahedral
Cell
a
Diamond lattice
Simple cubic lattice
Two-dimensional
representation of
the tetrahedral cell
Review Questions
What is Czochralski crystal growth?
What is a common wafer diameter?
How does “amorphous” differ from
“polycrystalline”?
How does “polycrystalline” differ from “single
crystal”?
Of the various items around you, determine
which ones fit into which of these three
categories?
How is the diamond lattice different from a
simple cubic lattice?