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Solid-State Electronics
 Textbook:
“Semiconductor Physics and Devices”
By Donald A. Neamen, 1997
 Reference:
“Advanced Semiconductor Fundamentals”
By Robert F. Pierret 1987
“Fundamentals of Solid-State Electronics”
By C.-T. Sah, World Scientific, 1994
 Homework: 0%
 Midterm Exam: 60%
 Final Exam: 40%
Solid-State Electronics
Chap. 1
1
Instructor: Pei-Wen Li
Dept. of E. E. NCU
Contents







Chap. 1
Chap. 2
Chap. 3
Chap. 4
Chap. 5
Chap. 6
Chap. 7
Solid-State Electronics
Chap. 1
Solid State Electronics: A General Introduction
Introduction to Quantum Mechanics
Quantum Theory of Solids
Semiconductor at Equilibrium
Carrier Motions:
Nonequilibrium Excess Carriers in Semiconductors
Junction Diodes
2
Instructor: Pei-Wen Li
Dept. of E. E. NCU
Chap 1. Solid State Electronics: A General
Introduction





Introduction
Classification of materials
Crystalline and impure semiconductors
Crystal lattices and periodic structure
Reciprocal lattice
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Introduction

Solid-state electronic materials:
–

Conductors, semiconductors, and insulators,
A solid contains electrons, ions, and atoms, ~1023/cm3.
 too closely packed to be described by classical Newtonian mechanics.

Extensions of Newtonian mechanics:
–
–
Quantum mechanics to deal with the uncertainties from small distances;
Statistical mechanics to deal with the large number of particles.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Classifications of Materials
 According to their viscosity, materials are classified into solids, liquid,
and gas phases.
Solid
Liquid
Gas
Low
Medium
High
Atomic density
High
Medium
Low
Hardness
High
Medium
Low
Diffusivity
 Low diffusivity, High density, and High mechanical strength means
that small channel openings and high interparticle force in solids.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Classification Schemes of Solids




Geometry (Crystallinity v.s. Imperfection)
Purity (Pure v.s. Impure)
Electrical Classification (Electrical Conductivity)
Mechanical Classification (Binding Force)
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Geometry
 Crystallinity
– Single crystalline, polycrystalline, and amorphous
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Geometry
 Imperfection
– A solid is imperfect when it is not crystalline (e.g., impure) or its atom are
displaced from the positions on a periodic array of points (e.g., physical defect).
– Defect: (Vacancy or Interstitial)
– Impurity:
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Purity
 Pure v.s. Impure
 Impurity:
– chemical impurities:a solid contains a variety of randomly located foreign atoms,
e.g., P in n-Si.
– an array of periodically located foreign atoms is known as an impure crystal with a
superlattice, e.g., GaAs
 Distinction between chemical impurities and physical defects.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Electrical Conductivity
Material type
Resistivity
(W-cm)
Conduction Electron
density (cm-3)
Examples
Superconductor
0 (low T)
0 (high T)
1023
Good Conductor
10-6 – 10-5
1022 – 1023
metals: K, Na, Cu, Au
Conductor
10-5 – 10-2
1017 – 1022
semi-metal: As, B,
Graphite
Semiconductor
10-2 – 10-9
106 – 1017
Ge, Si, GaAs, InP
Semi-insulator
1010 – 1014
101 – 105
Amorphous Si
Insulator
1014 – 1022
1 – 10
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Sn, Pb
Oxides
SiO2, Si3N4,
Instructor: Pei-Wen Li
Dept. of E. E. NCU
Mechanical Classification
 Based on the atomic forces (binding force) that bind the atom together,
the crystals could be divided into:
– Crystal of Inert Gases (Low-T solid):
Van der Wall Force: dipole-dipole interaction
– Ionic Crystals (8 ~ 10 eV bond energy):
Electrostatic force: Coulomb force, NaCl, etc.
– Metal Crystals
Delocalized electrons of high concentration, (1 e/atom)
– Hydrogen-bonded Crystals ( 0.1 eV bond energy)
H2O, Protein molecules, DNA, etc.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Binding Force
 Bond energy is a useful parameter to provide a qualitative gauge on
whether
– The binding force of the atom is strong or weak;
– The bond is easy or hard to be broken by energetic electrons, holes, ions, and
ionizing radiation such as high-energy photons and x-ray.
 In semiconductors, bonds are covalent or slightly ionic bonds. Each
bond contains two electrons—electron-pair bond.A bond is broken
when one of its electron is removed by impact collision (energetic
particles) or x-ray radiation, —dangling bond.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Semiconductors for Electronic Device Application

For electronic application, semiconductors must be crystalline and
must contain a well-controlled concentration of specific impurities.
 Crystalline semiconductors are needed so the defect density is low.
Since defects are electron and hole traps where e--h+ can recombine
and disappear, short lifetime.
 The role of impurities in semiconductors:
1. To provide a wide range of conductivity (III- B or V-P in Si).
2. To provide two types of charge carriers (electrons and holes) to
carry the electrical current , or to provide two conductivity types,
n-type (by electrons) and p-type (by holes)
 Group III and V impurities in Si are dopant impurities to provide
conductive electrons and holes. However, group I, II, and VI atoms
in Si are known as recombination impurities (lifetime killers)when
their concentration is low.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Crystal Lattices
 A crystal is a material whose atoms are situated periodically on
interpenetrating arrays of points known as crystal lattice or lattice
points.
 The following terms are useful to describe the geometry of the
periodicity of crystal atoms:
– Unit cell; Primitive Unit Cell
– Basis vectors a, b, c ; Primitive Basic vectors
– Translation vector of the lattice; Rn = n1a +n2b +n3c
– Miller Indices
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Basis Vectors
 The simplest means of representing an atomic array is by translation.
Each lattice point can be translated by basis vectors, â, bˆ , ĉ.
 Translation vectors: can be mathematically represented by the basis
vectors. Rn = n1 â + n2 + n3 ĉ, where n1, n2, and n3 are integers.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Unit Cell
 Unit cell: is a small volume of the crystal that can be used to represent
the entire crystal. (not unique)
 Primitive unit cell: the smallest unit cell that can be repeated to form
the lattice. (not unique) Example: FCC lattice
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Miller Indices
 To denote the crystal directions and planes for the 3-d crystals.
Plane (h k l)
Equivalent planes {h k l}
Direction [h k l]
Equivalent directions <h k l>
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Miller Indices
 To describe the plane by Miller Indices
– Find the intercepts of the plane with x, y, and z axes.
– Take the reciprocals of the intercepts
– Multiply the lowest common denominator = Mliller indices
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Example Use of Miller Indices
 Wafer Specification (Wafer Flats)
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
3-D Crystal Structures
 In 3-d solids, there are 7 crystal systems (1) triclinic, (2) monoclinic, (3)
orthorhombic, (4) hexagonal, (5) rhombohedral, (6) tetragonal, and (7)
cubic systems.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
3-D Crystal Structures
 In 3-d solids, there 14 Bravais or space lattices.
N-fold symmetry:
6-fold symmetry
With 2/n rotation, the
crystal looks the same!
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Basic Cubic Lattice
 Simple Cubic (SC), Body-Centered Cubic (BCC), and Face-Centered
Cubic (FCC)
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Surface Density
 Consider a BCC structure and the (110) plane, the surface density is
found by dividing the number of lattice atoms by the surface area;
Surface density = 2 atoms
(a1 )(a1 2 )
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Diamond Structure (Cubic System)
 Most semiconductors are not in the 7 crystal systems mentioned above.
 Elemental Semiconductos: (C, Si, Ge, Sn)
lattice constant a

1 1 1 
1 1 1
a  ( , , ), b  ( , , )
4 4 4
4 4 4

a b
1
  cos1   ,  cos1 ( )  109.4o
3
a || b |
(0,0,0)
=109.4o
(
1 1 1
, , )
4 4 4
1 1 1
( , , )
4 4 4
 The space lattice of diamond is fcc. It is composed of two fcc lattices
displaced from each other by ¼ of a body diagonal, (¼, ¼, ¼ )a
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Diamond Structure
 Or the diamond could be visualized by a bcc with four of the corner
atoms missing.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Zinc Blende Structure (Cubic system)
 Compound Semiconductors:
(SiC, SiGe, GaAs, GaP, InP, InAs, InSb, etc)
– Has the same geometry as the diamond structure except that zinc blende crystals
are binary or contains two different kinds of host atoms.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Wurzite Structure (Hexagonal system)
 Compound Semiconductors
(ZnO, GaN, ALN, ZnS, ZnTe)
– The adjacent tetrahedrons in zinc blende structure are rotated 60o to give the
wurzite structure.
– The distortion changes the symmetry: cubic hexagonal
– Distortion also increase the energy gap, which offers the potential for optical device
applications.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Reciprocal Lattice
 Every crystal structure has two lattices associated with it, the crystal
lattice (real space) and the reciprocal lattice (momentum space).
 The relationship between the crystal lattice vector ( aˆ, bˆ, cˆ ) and
reciprocal lattice vector ( Aˆ , Bˆ , Cˆ ) is
bˆxcˆ
cˆxaˆ
aˆxbˆ
ˆ
ˆ
ˆ
A  2
; B  2
; C  2
ˆ
ˆ
aˆ  bxcˆ
aˆ  bxcˆ
aˆ  bˆxcˆ
 The crystal lattice vectors have the dimensions of [length] and the
vectors in the reciprocal lattice have the dimensions of [1/length],
which means in the momentum space. (k = 2/)
 A diffraction pattern of a crystal is a map of the reciprocal lattice of the
crystal. A microscope image, if it could be resolved on a fine enough
scale, is a map of the crystal structure in real space.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Diffraction
Definition of scattering vector
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU
Reciprocal Lattice
Outing beam vector
Incident x-ray
beam vector,
Solid-State Electronics
Chap. 1

k'
  
G  k ' k
Reciprocal 
lattice vector G

k
30
Instructor: Pei-Wen Li
Dept. of E. E. NCU
Example
 Consider a BCC lattice and its reciprocal lattice (FCC)
 Similarly, the reciprocal lattice of an FCC is BCC lattice.
Solid-State Electronics
Chap. 1
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Instructor: Pei-Wen Li
Dept. of E. E. NCU