Transcript Introduction to Radar Systems

Drexel University
ECE Department
ECEE 302 Electronic
Devices
23 September 2002
ECEE 302: Electronic Devices
Lecture 1B. Solid State Device
Materials and Material
Growth
23 September 2002
BMF-Lecture 2-092302-Page -1
Copyright © 2002 Barry Fell
Drexel University
ECE Department
Outline
ECEE 302 Electronic
Devices
• Physical States of Matter (Solid, Liquid, Gas, Plasma)
• Electrical Classification of Materials (Conductor, Insulator, Semiconductor)
• Semi-Conductor Materials
• Mathematical Description of Crystal Lattices
–
–
–
–
–
primitive cell
simple cubic/body centered cubic/face centered cubic
Diamond Lattice/Zincblende
Close Packing
Miller Indices/direction indices
• Crystal Growth
– Bulk Crystal Growth
– Doping
– Epitaxial Crystal Growth
•
•
•
•
Lattice Matching
Liquid Phase
Vapor Phase
Molecular Beam Epitaxy
23 September 2002
BMF-Lecture 2-092302-Page -2
Copyright © 2002 Barry Fell
Drexel University
ECE Department
Physical States of Matter
ECEE 302 Electronic
Devices
• Solid State - Rigid structure. Strong coupling between atoms.
Fixed relation between atoms. Periodic arrangement of atoms.
Shape is fixed by structure
• Liquid State - Loose Structure. Weak coupling between molecules.
No Fixed relation between molecules. Shape is determined by
shape of vessel that contains liquid.
• Gaseous State - No over-arching structure. Collection of
individual molecules or atoms. No shape associated with a gas.
• Plasma State - Atoms are broken into individual constituants: ions
(positively charged) and electrons (negatively charged)
23 September 2002
BMF-Lecture 2-092302-Page -3
Copyright © 2002 Barry Fell
Drexel University
ECE Department
Electrical Description of Materials
ECEE 302 Electronic
Devices
• Three basic solid materials
– Conductor (of electricity or heat)
– Insulator (of electric current or heat)
– semi-conductor (properties depend on Temperature/Doping/etc)
• Physical Characteristics of Solid Materials are understood by the
“Band Theory of Solids”
• This course will focus on “Semi-Conductors”
• Conductors - easy to pass a current, relatively low loss.
• Insulators - high resistance, will not pass appreciable electric
current
• Semi-Conductors
– Described by Electron Band Theory of Solids
– Can be a good conductor or an insulator based on properties of the bands and
temperature
– Quantum Mechanics describes the theory and mechanisms of semi-conductors
23 September 2002
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Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Semi-Conductor Materials
• Semi-conductor properties are determined by electron mobility
(ease of movement)
• Electron mobility determined by valance of atom
• Semi-conductor material is from the periodic table column IV or
mixtures of Column III+IV or Column II+VI
• Doping (addition of other atoms to the crystal structure) enhances
the desired properties of semi-conductors
23 September 2002
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Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Periodic Table Column IV Materials
• Elemental Semi-conductors
– Si
– Ge
• IV Compound Semi-Conductors
– SiC
– SiGe
23 September 2002
BMF-Lecture 2-092302-Page -6
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Binary III-V Compound Semi-Conductors
•
•
•
•
•
•
•
•
•
23 September 2002
AlP
AlAs
AlSb
GaP
GaAs
GaSb
InP
InAs
InSb
BMF-Lecture 2-092302-Page -7
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Binary II-VI
•
•
•
•
•
•
23 September 2002
ZnS
ZnSe
ZnTe
CdS
CdSe
CdTe
BMF-Lecture 2-092302-Page -8
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Ternary and Quaternary Compound SemiConductors
• Ternary (3 element)
– GaAsP
– HgCdTe
– AlGaAs
• Quaternary (4 element)
– InGaAsP
23 September 2002
BMF-Lecture 2-092302-Page -9
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Crystal Structure
• Description of Solids is made possible for two reasons
– Translational symmetry Properties
– Rotational Symmetry Properties
• Crystal Structure Representation
– Translational Axes - directions within the crystal that describe the atomic
positions
– Unit Cell - cell that repeats itself within the crystal structure
– Primitive Cell - smallest unit cell
• Types of solids
– Crystalline - uniform distribution of atoms
– Amorphous - random position of atoms
– Polycrystalline - Multiple, randomly oriented, crystals
23 September 2002
BMF-Lecture 2-092302-Page -10
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Close Packing
• Assuming atoms are hard spheres, what percentage of a solid
volume is occupied by the atoms.
• Example: What is percentage of volume taken up by Si structure
Pack in gfraction of face- ce n te re d- cu bic(fcc)stru ctu reis de te rm in e das
follows:
Th e re are 4 atom s/ce ll
8 atom s at corn e rsare sh are dby 8 ce lls  1 atom
6 atom s on face s are e ach sh are dby 2 ce lls  3 atom s
Total atom s pe r u n it ce ll  4 atom s
Radiu s of atom , rSi 
a 2
4
 a3 23 2 
16



4

4 rSi3 
3  64 
Volu m eof Atom  3


  0.74  74%
Pack in gde n sity


3
3
Volu m eof ce ll
a
a
23 September 2002
BMF-Lecture 2-092302-Page -11
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Crystalline Basis Vectors
• Basis Vectors are special directions within the crystal
– Linear progression of atoms
– Linear progression of lines of atoms (planes)
– Linear progression of planes (volume)
a
b
a

 

r  la  mb  nc
a
c
b
23 September 2002
BMF-Lecture 2-092302-Page -12
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Unit Cell / Primitive Cell
• Smallest number of atoms needed to re-produce the regular solid
lattice structure
• Examples 

a
b
Unit Cell


Translation vectors, a and b
23 September 2002
BMF-Lecture 2-092302-Page -13
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Miller Indices
• Method of identifying planes within a Solid
• Procedure
– Find intercepts of planes in x, y, z axis
– Take reciprocals
– Multiply through to get smallest set of whole numbers
• Examples
2
1
1
1
1
1, ,  
,1,  

(1,0,0)

(0,1,0)
23 September 2002
1,1,2

1

 1,1,   2,2,1
2

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Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Direction Indices
• The vector that is perpendicular to the plane of interest
• Examples
2
1
1
1
1
Miller Indices
(1,0,0)
(0,1,0)
(2,2,1)
Direction Indices
[1,0,0]
[0,1,0]
[2,2,1]
23 September 2002
BMF-Lecture 2-092302-Page -15
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Crystal Growth (1 of 2)
• Bulk Crystal Formation
– Growth from Melt
• Czochralski Method
• Liquid Encapsulated Czochralski (LEC)
Method
– Localized Heating
– Zone Refining and Floating Zone
Growth
• distribution coefficient kd=(CS/CL)
– Seed Crystal
– Doping
23 September 2002
BMF-Lecture 2-092302-Page -16
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Impurities: distribution coefficient kd
• kd describes the ratio of concentration of the impurity to the melt
CS
Impurity conce ntrat
ion in Solid Phase
kd 

CL Impurity conce ntrat
ion in Liquid Phase
23 September 2002
BMF-Lecture 2-092302-Page -17
Copyright © 2002 Barry Fell
Drexel University
ECE Department
ECEE 302 Electronic
Devices
Crystal Growth (2 of 2)
• Epitaxy
–
–
–
–
Chemical Vapor Deposition (CVD)
Liquid Phase Epitaxy (LPE)
Metal-organic vaper-phase epitaxy (MOVPE or OMVPE)
Molecular Beam Epitaxy (MBE)
•
•
•
solid source
chemical beam
gas source MBE
– Lattice Matching
•
•
•
•
lattice matched
lattice mismatched
pseudomorphic layers
strained-layer super lattice (SLS)
23 September 2002
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Copyright © 2002 Barry Fell