Solid state electronic devices

540 Pages·2013·17.79 MB·english

by  Bhattacharya

SOLID STATE
ELECTRoniC
DEVICES
SECOND EDITION
D.K. Bhattacharya
Scientist
Solid State Physics Laboratory
New Delhi
Rajnish Sharma
Dean (Academics),
Chitkara University,
Himachal Pradesh
1
3
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First Edition published in 2007
Second Edition published in 2013
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ISBN-13: 978-0-19-808457-0
ISBN-10: 0-19-808457-9
Typeset in Times New Roman
by Time Digitech Private Limited, Noida
Printed in India by Yash Printographics, Noida 201301
About the Authors
D.K. Bhattacharya A PhD from the University of Delhi, he has over two decades of
experience as a practising semiconductor scientist including a long association with the
MEMS Division, Solid State Physics Laboratory, New Delhi. He has published more than
50 research papers in national and international journals and conference proceedings. He
is also the author of Engineering Physics (OUP, 2010).
Rajnish Sharma A PhD from Kurukshetra University and National Physical Laboratory,
New Delhi, he has served BITS, Pilani as a faculty for almost six years. He has successfully
handled a research project funded by the Ministry of Science and Technology, Government
of India and has presented his work at the MRS Symposium held at San Francisco and
at Risoe National Laboratory, Denmark. His current research interests are in the area of
device technologies for next-generation ICs and circuit design at radio frequencies.
Preface to the Second Edition
Solid state electronic devices are devices that are built entirely from solid materials
and in which electrons, or other charge carriers, are confi ned entirely within the solid
material. Prior to the use of solid state devices, most electronic devices used vacuum
tubes, in which electricity passed through various elements inside a heated vacuum
tube. In many applications, solid state devices have replaced vacuum tubes since they
last longer and are smaller, cheaper, and more effi cient and reliable.
While solid state devices can be built from crystalline, polycrystalline, and
amorphous solids, the building material is most often a crystalline semiconductor.
Common solid state devices include transistors, microprocessor chips, and dynamic
random access memory (DRAM) chips. The fi rst solid state device was the ‘cat’s
whisker’ detector which was fi rst used in 1930s as radio receivers. The transistor,
invented in 1947 by Bell Labs and named an IEEE Milestone in 2009, was the fi rst
solid state device to come into commercial use in the 1960s. More recently, the
integrated circuit (IC), the light-emitting diode (LED), and the liquid crystal display
(LCD) have evolved as further examples of solid state devices.
The semiconductor industry is seeing steady change, based on continued
technological innovations and the requirement of reducing cost. The next big
development in semiconductor manufacturing is the transition from 300 mm
wafers to 450 mm wafers, which can lead to reduction in die cost and subsequently
production cost. Other exciting recent developments in semiconductor industry are
the extreme ultraviolet (EUV) lithography and nano-chip technology. A nano-chip
can carry billions of transistors, and its applications include high-performance servers
and supercomputers, virtual reality and advanced electronic games, and ultra-fast
telecommunications devices. It is these types of applications that could lead to a new
revolution in how electronics goods are designed and manufactured.
Recognizing the importance of this industry in our everyday lives, this
second edition of Solid State Electronic Devices offers an improved coverage of
the fundamental concepts of solid state electronics. This edition is an attempt to
incorporate most of the feedback received from educators in terms of improvement
of content presented in the book.
About the Book
This book contains 14 chapters which provide a thorough coverage of solid state
electronic devices. Starting with the fundamentals of solid state physics such as electron
dynamics, growth and crystal properties of semiconductors, energy bands, and charge
carriers, the book goes on to the study of p-n junctions, metal–semiconductor contacts,
BJTs, and FETs (including JFET, MESFET, MOSFET, and HEMT technologies). An
analysis of special devices, such as opto-electronic devices, microwave devices, and
power devices, follows. Finally, the book covers ICs, MEMS, rectifi ers, and power
supplies.
vi Solid State Electronic Devices
Each chapter has been divided into small sections that are independent in
themselves. A unique feature of the book is the additional information in shaded
boxes at the end of relevant sections. These inputs offer a few extra facts outside the
limits of the curriculum to draw the interest and attention of students.
A large number of numerical problems along with answers and hints have been
provided at the end of each chapter. This is followed by a recapitulation of the salient
features of the chapter. Numerous review exercises and numerical problems along
with answers and hints have been provided as well. A list of references is presented
at the end of the book for those interested in further reading. A special attempt has
been made to include topics that are a part of courses offered by a large cross-section
of educational institutions.
New to the Second Edition
∑ New sections such as reciprocal lattice, band structure modifi cation, electrons and
holes in quantum wells, Early effect, short channel MOSFET I-V characteristics,
and photoluminescence and electroluminescence
∑ Detailed explanation and coverage
∑ New illustrations
Extended Chapter Material
Chapter 1 Applications of cathode ray tubes (CRTs) have been added.
Chapter 2 Reciprocal lattice, diffraction due to crystal planes, fl oatzone (FZ) method
of crystal growth, and four-probe method for the measurement of conductivity of
semiconductors are explained.
Chapter 3 The concept of phonon has been introduced and band structure modifi ca-
tion in semiconductors has been described.
Chapter 4 Deep impurity levels, Auger recombination process, and gradient in
quasi-Fermi levels have been described.
Chapter 7 Formation of practical ohmic contacts has been explained and a new
section on quantum confi nement of carriers has been introduced.
Chapter 8 Input and output characteristics of BJTs, Early effect in BJTs, thermal
runaway and thermal stability in BJTs, Kirk effect, and Webster effect have been
described.
Chapter 9 Signifi cantly expanded by introducing sections on short channel effect,
control of threshold voltage, substrate bias effects, sub-threshold characteristics,
equivalent circuits for MOSFET, MOSFET scaling and hot electron effects, drain-
induced barrier lowering, short channel and narrow width effect, gate-induced drain
leakage, and comparison of BJTs with MOSFETs.
Chapter 10 The phenomenon of photoluminescence has been explained.
Chapter 11 Two power semiconductor devices have been introduced – Gate Turn-off
Thyristor (GTO) and Insulated-Gate Bipolar Transistor (IGBT), and also the formula
to calculate intrinsic stand-off ratio has been included.
Preface to the second edition vii
Chapter 12 The process of photolithography, different etching techniques such as
wet etching and dry etching, and Moore’s law have been described.
Coverage
Chapter-wise details of content coverage are as follows:
Chapter 1 presents important aspects of electron dynamics, including the analysis
of motion of charged particles under the infl uence of electric and magnetic fi elds. The
last section of this chapter discusses the cathode ray tube in detail.
Chapter 2 presents the salient properties of semiconductor materials with a special
emphasis on the crystalline forms of these materials. Important concepts used for
classifying and defi ning crystal lattices have been outlined in this chapter. Bulk and
epitaxial growth techniques have also been included.
Chapter 3 introduces semiconductor physics, including energy bands and charge
carriers. E-k diagrams have been discussed in detail as they form the basis of
understanding the operation of many solid state electronic devices. It also presents a
comprehensive treatment of the two most important physical processes, namely drift
and diffusion of charge carriers. To make the treatment complete, a section has been
added to include graded impurity profi les.
Chapter 4 offers details about the nature and behaviour of excess carriers created by
external stimuli. A combination of drift and diffusion also governs the lives of excess
carriers. It also presents the very important concept of the continuity equation that
forms the core of any useful device physics model.
Chapter 5 initiates the study of solid state devices with the p-n junction. Beginning
with a brief discussion about the different methods used for fabricating p-n junctions,
the chapter also presents forward- and reverse-biased junctions.
Chapter 6 discusses the small-signal model of a p-n junction. An important aspect
of p-n junctions is the way it behaves when the polarity of the applied bias is suddenly
changed. A thorough treatment of transients that are critical to many applications is
provided in this chapter.
Chapter 7 discusses metal–semiconductor contacts or junctions, including ohmic
and Schottky contacts.
Chapter 8 discusses the bipolar junction transistor, without which the stupendous
growth in the fi eld of solid state electronics would not have been possible. The
treatment includes different models of the device along with an explanation of their
relative merits and demerits. Ordinary transistors cannot be operated at very high
frequencies. Methodologies involved in the design of high-frequency transistors are
presented in this chapter.
Chapter 9 focuses on the fi eld effect transistor which is a key ingredient for the
development of IC technology. Since the MOS structure forms the basis of this
device, the chapter also includes important features of this structure.
Chapter 10 describes opto-electronic devices, such as photovoltaic cells, photo-
detectors, LEDs, and laser diodes, which fi nd a variety of applications in the fi eld
viii Solid State Electronic Devices
of light wave communication. It also includes the basic principle of operation and
important semiconductor structures involved.
Chapter 11 develops a focused understanding of the special measures required
to enable solid state devices to handle high power, through the discussion of some
important aspects pertaining to power devices. Some special devices, such as
semiconductor-controlled rectifi ers (SCR) and unijunction transistors (UJT) are also
presented.
Chapter 12 discusses how the individual devices discussed up to Chapter 11 are put
together using standard processes to build widely used ICs. The three most important
technologies— namely MOSFET, MESFET, and bipolar technologies—are discussed
along with their salient features. This chapter also includes a discussion on micro-
electromechanical systems.
Chapter 13 focuses on some important microwave devices such as Gunn, IMPATT,
TRAPATT, and BARITT diodes. This chapter attempts to present the basic physics
of these devices so that students can understand their operation at microwave
frequencies.
Chapter 14 discusses some basic circuits such as rectifi ers, fi lters, and regulators
that combine to form power supplies, which are one of the most important application
areas of solid state devices. This is because all modern electronic systems need power
supplies to operate. The last section of this chapter deals with switched mode power
supply (SMPS), which is being increasingly used in various electronic systems.
Authors would be grateful for further suggestions and feedback with regard to
this edition.
D.K. Bhattacharya
Rajnish Sharma
Symbols
F Force tp0 Minority carrier hole lifetime
a Acceleration s Surface recombination velocity
m Mass V B uilt-in voltage
bi
W Work done C Depletion region capacitance
dep
V Voltage p Hole concentration in n-type
n
m Rest mass semiconductor
0
B Magnetic fi eld n Electron concentration in p-type
p
r Radius semiconductor
e Electronic charge L Diffusion length of electrons
n
p Pitch L Diffusion length of holes
1 p
D Defl ection s Conductivity
S D efl ection sensitivity for electric g Conductance
e
defl ection c D iffusion capacitance
d
S Defl ection sensitivity for r S pecifi c contact resistance
m C
magnetic defl ection I C ollector current
C
p Pressure I Base current
B
k Segregation coeffi cient I Emitter current
s E
y Wave function b Common-emitter current gain
m Effective mass A Voltage gain
eff V
n Equilibrium electron R D iffusion resistance
0 e
concentration C Emitter junction capacitance
je
p Equilibrium hole concentration C Parasitic capacitance between
0 p
n Intrinsic carrier concentration base and emitter
i
f(F) Fermi–dirac distribution function v Electron saturation velocity
S
N Effective density of states in R Collection-region series resistance
c C
conduction band C Collection-to-substrate
S
m * Density of states effective mass capacitance
n
N Effective density of states in C B-c junction capacitance
V BC
valence band f Cut-off frequency
T
N Donor concentration HBT Heterojunction bipolar transistor
d
N Acceptor concentration f Potential barrier for electron
a n
m Mobility injection
V Hall voltage f Potential barrier for hole injection
H p
R Hall coeffi cient V Collector supply voltage
H CC
D Diffusion coeffi cient of electrons V Base supply voltage
n BB
D Diffusion coeffi cient of holes t Delay time of transistor
p D
G Generation rate t Rise time of transistor
R
R Recombination rate t Storage time of transistor
S
E Band gap L Channel length of JFET
g
d Excess electron concentration W Channel width of JFET
n
d Excess hole concentration 2d Channel depth of JFET
p
E Trap energy V Gate voltage with respect to
t GS
tn0 Minority carrier electron lifetime source for JFET
xxii Solid State Electronic Devices
V Drain voltage with respect to V Potential drop across the
DS oxide(0)
source for JFET oxide for zero gate voltage
R R esistance f Surface potential for zero
s0
r R esistivity applied gate voltage
A A rea f Work function difference
ms
N D onor concentration V Voltage across oxide
d ox
W Width of depletion region Q Charge per unit area in the
d S
I D rain current semiconductor
D
V Drain–source voltage at r Charge density in
DS(sat) S
saturation semiconductor
e Dielectric constant of Q Charge per unit area in metal
S M
semiconductor E Electric fi eld across oxide
ox
V V oltage t Oxide thickness
ox
I P inch-off current e Dielectric constant of oxide
P ox
V Pinch-off voltage C Total capacitance
P
g D rain conductance C O xide capacitance
D ox
V T hreshold voltage C Depletion-layer capacitance
T J
HEMT High electron mobility C Minimum capacitance
min
transistor of MOS under strong
JFET J unction fi eld-effect transistor inversion
MODFET Modulation doped fi eld-effect V Flat band voltage
FB
transistor Q Charge per unit area within
o
MOS Metal–oxide–semiconductor oxide
E Conduction band edge E Electric fi eld within oxide
C 0
E I ntrinsic fermi energy level Q I nterface-trapped charge
Fi it
E Fermi energy level Q Fixed oxide charge
F f
E Valence band edge Q O xide-trapped charge
v ot
f P otential Q Mobile ionic charge
m
f Surface potential Z C hannel width
s
N A cceptor concentration g ¢ C hannel conductance
a D
fpF Difference between EFi MOSFET M etal–oxide–semiconductor
and EF for a p-type fi eld-effect transistor
semiconductor E Energy
W Maximum space-charge n F requency
dT
width h P lanck’s constant
fnF Difference between EFi C Velocity of light
and EF for an n-type Eg Energy band gap.
semiconductor In P hoton fl ux with frequency n
f ¢ M odifi ed work function of a A bsorption coeffi cient
m
metal g¢ Generation rate of EHP due
f Work function of metal to photons
m
c E lectron affi nity of I P hotocurrent
L
semiconductor I Short-circuit current
SC
c ¢ M odifi ed electron affi nity of V Open-circuit current
OC
semiconductor P Power
Symbols xxiii
V Voltage across solar cell under V Base-to-base voltage
m BB
maximum power condition V Peak-point voltage
P
I Current through solar cell V V alley-point voltage
m v
under maximum power G Conductance
condition R Sheet resistance

P Maximum power MEMS M icro-electromechanical
m
P Incident optical power system
in
h Conversion effi ciency of DRIE Deep reactive ion etching
solar cell LIGA LI (Röntgen lIthographie),
FF F ill factor G (Galvanik),
AM A ir mass A (Abformung).
R Series resistance SMPS Switched mode power
S
DE Conduction band step supply
c
DE Valence band step V Peak voltage
v m
s Conductivity R Load resistor
L
G Photo generation rate of v Load voltage
L L
excess carriers I Rms current
rms
v Drift velocity P A c power
d ac
t Electron transit time h C onversion effi ciency
n
G P hotoconductor gain PRV Peak reverse voltage
ph
t Transit time g R ipple factor
t
f Modulating frequency T T ime period
m
q C ritical angle w Angular frequency
C
n Refractive index I Zener diode current
Z
PT M aximum rated power Vi I nput voltage
R On-state resistance V Output voltage
ON o
R Channel contribution to P M aximum power
CH max
resistance t On time
ON
R D rain contact resistance RFI Radio frequency
D
R Thermal resistance interference
th
R Thermal resistance between IMPATT I mpact-avalanche
th(d-p)
device and package transit-time
R Thermal resistance between TRAPATT T rapped-plasma avalanche-
th(p-s)
package and heat sink triggered-transit
R Thermal resistance between BARITT Barrier-injected transit-time
th(s-a)
heat sink and ambient m Mobility in central valley
G
P Maximum power dissipation v Avalanche-zone velocity
D(max) Z
T Device temperature MSM M etal–semiconductor–metal
dev
T Maximum junction
j(max)
temperature