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Semiconductor Physics: Units, Crystal Structure, and Doping, Lecture notes of Physics

A comprehensive overview of semiconductor physics, focusing on units, crystal structure, and doping. It explains the importance of consistent units in semiconductor physics, outlines the different types of solids, and delves into the concept of doping, which involves adding impurities to semiconductors to alter their electrical conductivity. The document also discusses the different types of atomic bonding in solids, including ionic, covalent, metallic, and van der waals bonding.

Typology: Lecture notes

2023/2024

Uploaded on 12/25/2024

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PHYSICS 1070
SEMICONDUCTOR PHYSICS
UNITS in SEMICONDUCTOR PHYSICS
In this course you’ll encounter a variety of units, both Si and non-SI, stated with
metric prefixes and in scientific notation. Before substituting quantities into
equations all the units should be consistent…all in the same form…. so you’ll need
to be able to easily convert from one form to another. Appendix B of your
textbook also contains information about SI units, conversion factors and
constants. A reference page of constants, conversion factors and SI prefixes has
been provided on your myCourselink site…..this table will also be available for
your tests and final exam.
Dimension
Unit Name
Symbol
Length
meter
m
Time
second
s
Mass
kilogram
kg
Electric Current
ampere
A
Thermodynamic Temperature
kelvin
K
Amount of Substance
mole
mol
Luminous Intensity
candela
cd
The current and historical definitions of the base units are described on the NIST
(National Institute of Standards and Technology, U.S. Department of Commerce)
website; http://physics.nist.gov/cuu/Units/units.html .
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PHYSICS 1070

SEMICONDUCTOR PHYSICS

UNITS in SEMICONDUCTOR PHYSICS In this course you’ll encounter a variety of units, both Si and non - SI, stated with metric prefixes and in scientific notation. Before substituting quantities into equations all the units should be consistent…all in the same form…. so you’ll need to be able to easily convert from one form to another. Appendix B of your textbook also contains information about SI units, conversion factors and constants. A reference page of constants, conversion factors and SI prefixes has been provided on your myCourselink site…..this table will also be available for your tests and final exam. Dimension Unit Name Symbol Length meter m Time second s Mass kilogram kg Electric Current ampere A Thermodynamic Temperature kelvin K Amount of Substance mole mol Luminous Intensity candela cd The current and historical definitions of the base units are described on the NIST (National Institute of Standards and Technology, U.S. Department of Commerce) website; http://physics.nist.gov/cuu/Units/units.html.

Combinations of the base units are called derived units eg. m^2 for a unit of area. Some derived units are re- named eg. the units for force obtained from Newton’s second law → → F = ma, where both force and acceleration are vectors, is the derived unit kg-m/s^2. This derived unit is called the newton and given the symbol N. The SI base units may be conveniently used for very small and very large numbers by utilizing the metric prefixes which give us multiples of 10 or 10-^1 when expressed in scientific notation. SI Prefixes and Base Units 1024 yotta Y 10 -^1 deci d 1021 zetta Z 10 -^2 cent 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 Some non-SI units are still in use, such those which were introduced in the first tutorial eg. the energy unit called the electron-volt (eV), the unified atomic mass unit (u) for mass and a unit of length called the angstrom. atomic mass unit 1 u = 1.66 x 10-^27 kg electron volt 1 eV = 1.602 x 10-^19 J angstrom 1 Å = 1 x 10-^10 m magnetic field 1 T = 1 x 10^4 G

Fig. 1.5 Semiconductor Physics and Devices, Donald A. Neamen Single crystal materials have long-range order and are used in the production of semiconductor devices. The success in fabricating very large scale circuits (VLSI) is due in part to the development of the pure single-crystal growing techniques, described in your textbook in Section 1.7.1. Crystals must be grown to be as defect free as possible to achieve the desired electrical properties. Defects and impurities will affect the electrical properties of the crystal. All crystals will be distorted by lattice vibrations which are the source of polarons. The electrical characteristics of semiconductors and other materials are altered by lattice vibrations. More examples of types of defects and imperfections are shown below in a 2-D lattice;

  • Point Defects - Vacancy and Interstitial Defects; Fig. 1.21 An Introduction to Semiconductor Devices, Donald Neaman
  • Line/Plane Defects; Fig. 1.22 An Introduction to Semiconductor Devices, Donald Neaman
  • Substitutional and Interstitial Impurities Fig. 1.23 An Introduction to Semiconductor Devices, Donald Neaman MORE CHARACTERISTICS OF SEMICONDUCTORS The conductivity of semiconductors is strongly affected by chemical ‘impurities’. Intrinsic semiconductors such as silicon and germanium are not very good conductors but the conductivity changes dramatically when minute amounts of selected impurities are added; Group III indium, tellurium, gallium, boron Group V phosphorus, antimony, bismuth 1 impurity atom per billion atoms of Si or Ge changes the conductivity by a factor of 1000. Effects are so extreme that care must be taken to avoid undesirable contamination during manufacture. The advantage of this effect is that semiconductors can be ‘doped’ to increase their conductivity by selectively adding impurities that will increase the number of charge carriers to achieve desired electrical characteristics.