an introduction to semiconductor devices - ::...
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An Introduction toAn Introduction toSemiconductor DevicesSemiconductor Devices
Donald Neamen
Images and illustrations from supplements of “An Introduction to Semiconductor
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Images and illustrations from supplements of An Introduction to Semiconductor Devices” , 4th Ed., Mc Graw Hill were used for this lecture materials.
Semiconductor MaterialsSemiconductor Materials
Elemental SC - Group 4 elements : C, Si, Ge
Alloysp , ,
- Sn, Pb?
Compound SC
- Binary : Si-Ge
- Ternary : (Al,Ga)As, (Al,In)As, (Cd,Mn)Te,Ga(As,P), (Ga,In)As, (Ga,In)P, (Hg,Cd)TeCompound SC
- Intermetallic compound - IV-IV(Si-Ge, Si-C) - III-V(Al-P,As,Sb; Ga-N,P,As,Sb; In-N,P,As,Sb), BN
(Ga,In)As, (Ga,In)P, (Hg,Cd)Te- Quaternary : (Al,Ga)(As,Sb), (Ga,In)(As,P)
III V(Al P,As,Sb; Ga N,P,As,Sb; In N,P,As,Sb), BN- II-VI(Zn-S,Se,Te; Cd-S,Se,Te; Hg-Se,Te), MgO
I II III IV V VI VII VIII
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
Ca/Zn
H Ti Pb Bi
a g S S C
K Ga Ge As Se Br Kr
Cd In Sn Sb Te
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Hg Ti Pb Bi
Semiconductor HistorySemiconductor Historyyy
1833; Fist semiconducting property of Ag2S by Faraday1833; Fist semiconducting property of Ag2S by Faraday1873; Discovery of photoconductivity of Se by Smith 1874; Observation of rectification by Braun 1879 Di f H ll ff t ( l t t t di d)1879; Discovery of Hall effect (electron not yet discovered)1911; The term “semiconductor” introduced by Konigsberg & Weiss1927; copper oxide rectifier by Grondahl & Geiger1931; photocell by Bergmann1939; Development of microwave (Si)1940s; IR detectors of sulphide, selenide, telluride; p , ,1949; Discovery of transistor action by Bardeen & Brattain 1950; Invention of transistor by Shockley, First amorphous semiconductor (α-Se) ~ present;~ present;IC (electronic industry), solid state laser, organic semiconductors, artificial compound semiconductors
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Physical Constants and unitsPhysical Constants and unitsyy
Avogadro's number: NA .6.02 10 23
Boltzmann's constant k ..1.38 10 23 jouleK
Electronic charge (magnitude): e ..1.60 10 19 ( )coul
Free electron rest mass me ..9.1094 10 31 ( )kg
Permeability of free space: μ0 ..( ).4 π 10 7 henrymm
Permittivity of free space ε0 ..8.854 10 14 faradcm
Planck's constant: h ..6.625 10 34 ( ).joule sec
Proton rest mass mp ..1.67 10 27 ( )kg
Speed of light in vacuum: c ..2.998 10 10 cmsecsec
eV ..1.60 10 19 joule (electron-volt) meV .10 3 eV
μsec 10 6 sec nA 10 9 amp pA 10 12 amp V volt
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μsec .10 sec nA .10 amp pA .10 amp V volt
μm .10 6 m nm .10 9 m Angstrom .10 10 m Å .10 10 m
Types of SolidsTypes of Solidsypyp
Amorphous materials (for instance, glass and rubber) have order within a few atomic or molecular dimensionsfew atomic or molecular dimensions .
Polycrystalline materials have a high degree of order over many atomic or molecular dimensions These orderedmolecular dimensions. These ordered regions, or single-crystal regions , vary in size and orientation with respect to one another. The single-crystal regions are called grains and are separated from one another by grain boundaries.Single-crystal materials ( for example, silicon, copper, and table salt) have a very high degree of order, or regular geometric periodicity, throughout their entire volume. The advantage of a gsingle-crystal material is that, in general, its electrical properties are superior to those of a nonsingle-crystal material, since grain boundaries tend to degrade
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since grain boundaries tend to degrade the electrical characteristics.
SiOSiO22/Si/Si22
HRXTEM view of Si/SiO2
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Defects in MaterialDefects in Material
Point defect (0-D) Surface defect (2-D)Grain boundary
Vacancy
Interstitial
Grain boundary
ex) ImpuritiesSubstitutional
Interstitialimpurity
Substitutionalimpurity Bulk defect (3-D)
Precipitate
Line defect (1-D)
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Edgedislocationline
Point DefectsPoint Defects
A vacancy in the crystal. A substitutional impurity in the crystal. Theimpurity atom is larger than the host atom.
A substitutional impurity inthe crystal. The impurity atomis smaller than the host atom
An interstitial impurity in the crystal. Itoccupies an empty space between host atoms.
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is smaller than the host atom.
Line DefectsLine Defects
AC
A screw dislocation in a crystal.
D
Dislocation line
CompressionTension
A BDislocation
y
A BDislocationlineA edge dislocation in a crystal is a line defect
which is accompanied by lattice distortion and hence a lattice strain around it.
D C
Atoms in theupper portion.
Atoms in thelower portion .
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The screw dislocation in as viewed from above.
Line DefectsLine Defects
InGaAs/AlGaAs QWs
dislocations
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Surface DefectsSurface Defects
CrystalliteNuclei y
Liquid
Self interstitial typeatomForeign impurity
(b)
Liquid
( )
Strainedbond
Grainboundary
Void, vacancySelf-interstitial typeatom(b)(a)
Brokenbond(danglingbond)
GrainboundaryGrainGrainboundary
(c)Solidification of a polycrystalline solid from the melt. (a) Nucleation. (b) Growth (c) The solidified polycrystalline solid For simplicity cubes
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Growth. (c) The solidified polycrystalline solid. For simplicity, cubes represent atoms.
Primitive and Unit cellsPrimitive and Unit cells
LatticeUnit cell
: Periodic arrangement of atoms in the crystal→ Dots can be used for representing the atomic arrays: Lattice
Primitive unit cell
3-D unit cell
Primitive unit cell
Two dimensional lattice
- Unit cell : A small of the crystal that can be used to reproduce the entire crystal r = p a + q b + s c (p, q, s = integers)
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Basic Crystal StructuresBasic Crystal Structuresyy
Cubic Lattices
Simple Cubic (SC) Body-Centered Cubic (BCC) Face-Centered Cubic (FCC)
(000) (000)1 1 12 2 2
⎛ ⎞⎜ ⎟⎝ ⎠
(000) 1 1 02 2
⎛ ⎞⎜ ⎟⎝ ⎠
1 102 2
⎛ ⎞⎜ ⎟⎝ ⎠
1 102 2
⎛ ⎞⎜ ⎟⎝ ⎠
Q1: How many atoms are included in each unit cell ?Q2: What are the packing densities ?
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Miller indexMiller index
cUnitCell Geometry
zz
Unit cellLattice direction
cy
c
bOα
βc
yyxo
Pzo [121]
xba
aγ
A parallelepiped is chosen to describe geometry of ait ll W li th d ith th d f
abx
yyoo
Identification of a direction in a crystal
[001] [111]
unit cell. We line the x, y and z axes with the edges ofthe parallelepiped taking lower-left rear corner as theorigin
[010]
[100]
[010]
[110] [110]
-a-yax
y
[ ] [110] [ ][111]
[111]
[111][111]
Directions in cubic crystal system
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[111] [111]
[111]
[111] Family of <111>directions
Crystal plane and Miller indexCrystal plane and Miller indexy py p
Index of Plane
1 1 1 , , p q s
Plane⎛ ⎞
= ⎜ ⎟⎝ ⎠
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Crystal plane and Miller indexCrystal plane and Miller indexy py p
z(010) (010) (010)(010)
z
y
(010) (010)
(010)
y
Miller Indices (hk ):1 1
11 (210)1
2
z intercept at ∞ b
cx intercept at a/2
∞
(001) (110)xx
ax
y
x intercept at /2
y intercept at bUnitcell (100) z
Identification of a plane in a crystal (111)
y
(110)z
y
(111)
- z
x
x
- yy
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Various planes in cubic lattices
The Structure of Solids and Surfaces
Bulk termination : FCC
FCC (110)FCC (110)
FCC (100) FCC (111)
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The Structure of Solids and Surfaces
Bulk termination : BCC
BCC (110)BCC (110)
BCC (100) BCC (111)
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Crystal plane and Miller indexCrystal plane and Miller indexy py p
ex) Calculate the surface density of (110) plane in fcc. ao = 4.5 Å.
( ) 22 atoms 2 atomsSurface density = = Q1: Surface density of (111) plane in fcc
( )( ) ( )280 0
14 2
ya 2a 2 4.5 10
= 6.98 10 atoms/cm
−× ×
×
y ( ) p
Q2: ao = 4.75 Å. Calculate the surface densities
of (100) and (110) planes in bcc.
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Semiconductor StructureSemiconductor Structure
Diamond Cubic Structure
[ ]fcc fcc+ •14 111
Q1: How many atoms in unit cell ?Q2: Coordinates of atoms in unit cell ?Q ?
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Q3: What are the packing densities ?
Semiconductor StructureSemiconductor Structure
Diamond cubic structure has
- 8 atoms/unit cell- atomic packing factor = ~34 %- covalent bonding, tetragonal unit, 4 nearest neighborsg, g , g
a0
0 01/2
1/43/4
a0/2
3/41/4
1/21/2 0
[ ]1
00 1/2
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[ ]fcc fcc+ •14 111
Semiconductor StructureSemiconductor Structure
Zincblende structure Differs from the diamond structure only in that there are two types of atoms in the lattice
- GaAs crystal structurefcc 4 Ga atoms
[ ]14 111 fcc• 4 As atoms, or vice vera.[ ]4 f 4 As atoms, or vice vera.
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Semiconductor GrowthSemiconductor Growth
Purity & Doping
Purity : unintentionally doped (undesired) impurities- Purity : unintentionally doped (undesired) impuritiesSi : 1 per 109 Si atoms
- Dopants : intentionally added impuritiesPractical functioning of devicesPractical functioning of devices
Crystal Growth
Electronic grade poly Si- Electronic grade poly-Si
Silica Impureili SiCl4 Ultrapure
SiCl Poly-Sisilicon SiCl4 SiCl4 Poly Si
Reduction Chlorination Distilation H-Reduction
- Single crystal growingCzochralski method
Single crystal seed
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Crystal pulling and rotation
Semiconductor GrowthSemiconductor Growth
(Mitsubishi website at http://www.egg.or.jp/MSIL/english/index-e.html)
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Semiconductor GrowthSemiconductor Growth
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HomeworkHomework
Ch.1
4 (d), 7, 10, 14, 16, 19, 25
Due date:
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