L8 Semiconductors and diodes_part1
Page 1: Introduction to Semiconductors and Diodes
Topic 4: Semiconductors and Diodes.
Reference: Web Elements for crystal structure of silicon.
Page 2: Understanding Diodes and Transistors
Diode: A semiconductor device allowing current flow in one direction; key in rectification (converting AC to DC).
Transistor: Acts as an electronic switch in integrated circuits (IC) for processors and memories. Used widely in power electronics and amplifiers.
Page 3: Integrated Circuits (IC)
Integrated Circuit (IC): Electric circuit on a small semiconductor substrate (usually silicon) containing numerous components.
Examples of transistors in modern microchips:
Snapdragon 855+: 6.7 billion transistors.
Apple A13 Processor (iPhone 11 Pro): 8.5 billion transistors.
Kirin 990 (2019): 10.3 billion transistors.
Page 4: Composition of ICs
IC Definition: Microelectronic circuits that assemble electronic components as a single unit.
Contains both active devices (transistors and diodes) and passive devices (capacitors and resistors) on a semiconductor substrate.
Size of IC can range from a few square centimeters to millimeters.
Page 5: Applications of Integrated Circuits
ICs are made for various purposes, including:
Processors and memories
Amplifiers
Power electronics
Control systems
Radio technology
Sensors
Micro-electromechanical systems (MEMS).
Silicon chips are often encapsulated for environmental protection.
Page 6: Diode Lasers
Diode Laser: Special application of LEDs, used in optical data transmission (e.g., backbone Internet connections).
Page 7: Solar Cells
Solar Cell: Incorporates external energy into the pn-junction.
Light radiation creates electron/aperture pairs, generating voltage at the pn-junction.
Resulting voltage is typically around 1V; higher voltage requires series connections of cells.
Page 8: Light Emitting Diodes (LEDs)
LED: A semiconductor device emitting light when current flows through it.
Applications: Indicator lights, general lighting.
Page 9: Heat Flux Sensors
Silicon-based heat flux sensor developed with LUT and VTT Micronova.
Features single chip specimens and silicon wafers with multiple designs.
Page 10: Significance of Semiconductors
Semiconductors are fundamental to modern electronics.
All electronic devices are built with semiconductor components such as processors, amplifiers, and sensors.
Overview of semiconductor physics and diodes.
Page 11: Properties of Semiconductors
Semiconductors are not isolated substances but materials that can shift between conductive and non-conductive states.
Conductivity can be regulated by temperature or external electric fields.
Material properties can be altered by adding other substances.
Page 12: Grouping of Conductive Materials
Materials based on electric conductivity:
Conductors: e.g. copper, aluminum.
Semiconductors: e.g. silicon, germanium.
Insulators: e.g. polythene.
Differences in conductivity arise from electron movement.
Page 13: Electrical Properties of Conductors and Insulators
Conductors: Have free electrons, enabling electrical flow when an electric field is applied.
Insulators: Electrons are tightly bound, limiting electricity conduction.
Page 14: Properties of Semiconductors
At low temperatures, semiconductors behave like insulators; as temperature increases, electrons gain mobility, acting as conductors.
Page 15: Electron Band Theory
Describes electrons by energy levels.
Electrons positioned on an energy scale, experiencing specific ranges called energy bands.
The lowest band is the valence band, which binds atoms.
Page 16: Valence Electrons and Atomic Structure
Valence electrons dictate the electrical properties of solids.
In materials, electrons interact to form energy bands.
Page 17: Silicon Structure
Silicon's atomic structure consists of three electron shells with a total of 14 electrons.
Page 18: Periodic Table Overview
Groups of elements and their classifications in the periodic table, including transition metals and other nonmetals.
Page 19: Semiconductor Materials
Main semiconductor materials include:
Silicon (Si)
Gallium arsenide (GaAs)
Germanium (Ge)
Silicon is the predominant semiconductor material; carbon is emerging as significant material for future applications.
Page 20: Carbon as a Semiconductor Material
Carbon forms are being integrated into semiconductor materials in the 2020s.
Graphene, discovered in 2010, offers high-speed electrical flow, capable of 100 GHz switching frequencies (on-off).
Page 21: Crystal Structure of Semiconductors
Semiconductor atomic structures typically form crystal lattices with covalent bonds.
The octet rule guides chemical bonding, where atoms seek stability through complete outer shells.
Page 22: Silicon's Electron Behavior
Silicon atoms have 4 valence electrons, forming covalent bonds with neighboring atoms, sharing electrons.
Thermal vibrations can break these bonds, generating free electrons (charge carriers).
Page 23: Conductive Properties of Pure Semiconductors
In pure semiconductors, thermal vibrations generate charge carriers (electrons and holes), although they are poor conductors at room temperature.
Page 24: Thermal Vibration Effects
Thermal vibrations affect silicon's structure and conductivity.
Page 25: Conductors vs. Insulators
Classification based on energy bands:
Conductors: minimal band gap (< 0.2 eV).
Semiconductors: narrow band gap (0.2 - 3 eV).
Insulators: wide band gap (> 3 eV).
Page 26: Electric Current Generation
Electric current (electron flow) arises from free electrons not bound to the valence band, with energy in the conduction band.
Metals conduct well due to overlapping bands; insulators require significant energy for conduction.
Page 27: Conductivity in Semiconductors
Narrow forbidden energy gap means minimal energy is needed to make semiconductors conductive.
Conductivity can increase with temperature, external electric fields, or light.
Page 28: Charge Carrier Movement
At normal temperatures, some electrons gain enough energy to cross the band gap, creating conduction electrons and holes.
Mobility of conduction holes and electrons enhances electrical conductivity.
Page 29: Electron Transition to Conduction Band
When valence electrons gain energy, they move to the conduction band, enabling electricity conduction.
Metals conduct easily; insulators require substantial energy.
Page 30: Pure vs. Intrinsic Semiconductors
Pure semiconductors, composed only of intrinsic materials, have limited practical use in modern components.
Page 31: Doping in Semiconductors
Charge carrier concentration can be increased by introducing small amounts of impurities.
A typical mixing ratio is 1:106-108, maintaining material's integrity while modifying electrical properties.
Page 32: Group V Doping Elements
Doping elements (e.g., phosphorus) have 5 valence electrons, introducing extra electrons into the semiconductor lattice.
Page 33: n-Type Semiconductors
Free charges from impurities in n-type semiconductors are predominantly electrons, making them majority carriers.
Page 34: Group III Doping Elements
Group III doping elements (e.g., boron) create holes in the crystal lattices that facilitate positive charge movement.
Page 35: p-Type Semiconductors
In p-type semiconductors, holes are the majority carriers, providing paths for electric currents.
Page 36: Diode Functionality
Overview of how diodes work and their functionality via the PN junction.
Page 37: Conclusion
Conclusion of Part 1 on Semiconductors.