Fundamentals of learn how to Semiconductors can easily be mani pulated to become conducting or insulating materials and can change their conductive properties
This slide give you idea about the atomic structure, classification of solids based on valance electron, free electron, energy band description, why the silicon is used as semiconductor substance compare to germanium, semiconductor and its types.
Energy bands consisting of a large number of closely spaced energy levels exist in crystalline materials. The bands can be thought of as the collection of the individual energy levels of electrons surrounding each atom. The wavefunctions of the individual electrons, however, overlap with those of electrons confined to neighboring atoms. The Pauli exclusion principle does not allow the electron energy levels to be the same so that one obtains a set of closely spaced energy levels, forming an energy band. The energy band model is crucial to any detailed treatment of semiconductor devices. It provides the framework needed to understand the concept of an energy bandgap and that of conduction in an almost filled band as described by the empty states.
Fundamentals of learn how to Semiconductors can easily be mani pulated to become conducting or insulating materials and can change their conductive properties
This slide give you idea about the atomic structure, classification of solids based on valance electron, free electron, energy band description, why the silicon is used as semiconductor substance compare to germanium, semiconductor and its types.
Energy bands consisting of a large number of closely spaced energy levels exist in crystalline materials. The bands can be thought of as the collection of the individual energy levels of electrons surrounding each atom. The wavefunctions of the individual electrons, however, overlap with those of electrons confined to neighboring atoms. The Pauli exclusion principle does not allow the electron energy levels to be the same so that one obtains a set of closely spaced energy levels, forming an energy band. The energy band model is crucial to any detailed treatment of semiconductor devices. It provides the framework needed to understand the concept of an energy bandgap and that of conduction in an almost filled band as described by the empty states.
The following presentation is a part of the level 4 module -- Electrical and Electronic Principles. This resources is a part of the 2009/2010 Engineering (foundation degree, BEng and HN) courses from University of Wales Newport (course codes H101, H691, H620, HH37 and 001H). This resource is a part of the core modules for the full time 1st year undergraduate programme.
The BEng & Foundation Degrees and HNC/D in Engineering are designed to meet the needs of employers by placing the emphasis on the theoretical, practical and vocational aspects of engineering within the workplace and beyond. Engineering is becoming more high profile, and therefore more in demand as a skill set, in today’s high-tech world. This course has been designed to provide you with knowledge, skills and practical experience encountered in everyday engineering environments.
The following presentation is a part of the level 4 module -- Electrical and Electronic Principles. This resources is a part of the 2009/2010 Engineering (foundation degree, BEng and HN) courses from University of Wales Newport (course codes H101, H691, H620, HH37 and 001H). This resource is a part of the core modules for the full time 1st year undergraduate programme.
The BEng & Foundation Degrees and HNC/D in Engineering are designed to meet the needs of employers by placing the emphasis on the theoretical, practical and vocational aspects of engineering within the workplace and beyond. Engineering is becoming more high profile, and therefore more in demand as a skill set, in today’s high-tech world. This course has been designed to provide you with knowledge, skills and practical experience encountered in everyday engineering environments.
A Strategic Approach: GenAI in EducationPeter Windle
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This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
2. Learning Outcome
2
• At the end of this topic, the student should be able to:
1. Understand material classification, atomic structures, energy band, covalent
bonds and conduction in semiconductors.
2. Understand the concept of free electrons and holes as carriers.
3. Explain types of semiconductor : Intrinsic and Extrinsic
4. Explain doping process for the semiconductor material.
5. Explain the formation of P-type, N-type material.
6. Describe the process of depletion region in semiconductor and P-N junction
formation
3. Atomic structures
• Construction of every discrete solid-state electronic device or IC begin with highest
quality semiconductor material
• Semiconductors (S/C) are a special class of elements having a conductivity between
good conductor and insulator
• Two classes of S/C material :
• Single crystal – repetitive crystal structure i.e Ge, Si
• Compound – constructed of 2 or more S/C materials of different atomic structure
i.e GaAs, CdS, GaN, GaAsP
• Most frequently used in electronic devices - Germaniun (Ge), Silicon (Si) and Galium
Arsenic (GaAs)
4. Crystal structure of silicon Compound : Crystal structure of GaN (Gallium Nitride)
5. • Atoms are bound together to form a crystalline structure
• Fundamental components of atoms are electron, proton and neutron
• In the lattice structure, neutron and protons form the nucleus
• Electrons appear in fixed orbits around the nucleus
• Bohr model of atomic structure are shown in Fig.1
• Si has 14 orbiting electrons, Ge has 32, Gallium has 31 and arsenic has 33 orbiting
electron respectively
• Si and Ge has four valence electrons, Ga has three and As has five valence electrons
• Atom with four valence electrons called tetravalent, those with three are called trivalent
and those with five are called pentavalent.
7. Covalent Bonding
• In a pure Si or Ge crystal, the four valence electrons of one atom form a
bonding arrangement with four adjoining atoms.
• This bonding of atoms, strengthened by the sharing of electrons is called
covalent bonding.
• Since GaAs is a compound semiconductor, there is sharing between two
different atoms.
• The sharing between GaAs is five electron provided by the As atom and three
by the Ga atom.
• Covalent bonding of the Silicon atom and GaAs crystal are shown in Fig. 2
9. Free electrons
•Covalent bond will result in a stronger bond between the valence electrons and their
parents atom
•However, it is still possible for the valence electrons to absorb sufficient kinetic
energy (from external such heat from surrounding medium) to break the covalent
bond - cause ‘free’ state
•Free state refer to any electron that has separated from the fixed lattice structure
•At room temperature there are approximately 1.5x1010 free carriers in 1 cm3 of
intrinsic Silicon material (15 billion electrons in a space smaller than small sugar
cube)
•The free electrons is a material due only to external cause reffered as intrinsic
carriers.
10. • Interesting difference between semiconductors and conductors is their
reaction to the application of heat.
• For conductors, the resistance increase with an increase in heat – due to
number of carriers in a conductor do not increase significantly with
temperature but their vibration pattern
• Semiconductor materials however exhibit an increased level of conductivity
with the application of heat.
• As temperature rises, an increasing number of valence electrons absorb
sufficient thermal energy to break covalent bond and contribute to the
number of free carriers.
11. Energy levels
• Within the atomic structure of every isolated atom there are specific energy levels
associate with each shell and orbiting electron.
• The farther an electron is from the nucleus, the higher is the energy state, and any
electron that has left its parent atom has a higher energy state than any electron in
the atomic structure.
• Only specific energy levels can exist for the electrons in the atomic structure of an
isolated atom.
• The result is a series of gaps between allowed energy levels where carriers are not
permitted.
12. Energy levels
Figure 3. : Energy levels (a)
discrete levels in isolated
atomic structures
Figure 3 (b) :Conduction and
valence bands of an insulator,
a semiconductor and a
conductor
13. • An electron in the valence band of Silicon must absorb more
energy than one in the valence band of Germanium to become a
free carrier.
• Similarly an electron in the valence band of GaAs must gain more
energy than one in Silicon or Ge to enter the conduction band.
• This difference in energy gap requirements reveals the sensitivity
of each type of semiconductor to changes in temperature.
• This sensitivity to changes in energy level can have positive and
negative effects.
• For transistor networks, where stability is a high priority, this
sensitivity to temperature or light can be a detrimental factor.
14. • The wider the energy gap, the greater is the possiblility of energy
being released in the form of visible or invisible light waves
• For conductors, the overlapping of valence and conduction bands
essentially results in all the additional energy picked up by the
electrons being dissipated in the form heat.
• Similarly, for Ge and Si since the energy gap is small, most of the
electrons that pick up sufficient energy to leave the valence band
end up in conduction band and the energy is dissipated in the
form of heat.
• However for GaAs the gap is sufficintly large to result in
significant light radiation.
15. • As the atoms of a material are brought closer together to form the crystal lattice structure,
there is an interaction between atoms
• The electrons of a particular shell of an atom having slightly different energy levels from
electrons in the same orbit of an adjoining atom.
• The result is an expansion of the fixed, discrete energy levels of the valence electrons (Fig.3a)
to bands as shown in Fig. 3b.
• The valence electrons in a Silicon material can have varying energy levels as long as they fall
within the band of Fig. 3b
• Fig. 3b clearly reveals that there is a minimum energy level associated with electrons in the
conduction band and a max energy level of electrons bound to the valence shell of the atom
• Between the two is an energy gap that the electron in the valence band must overcome to
become free carrier.
• That energy gap is different for Ge, Si and GaAs; Ge has the smallest gap and GaAs has the
largert gap.
18. Semiconductor Material Classification
A semiconductor is a material that has intermediate conductivity between a conductor and an insulator
Semi = Half
Conductor = Material that can carry electricity
S/C Material
Intrinsic
(Pure Si & Ge)
Extrinsic
(doped with impurities)
N-type
-doped with pentavalents
impurities
-donor impurities
-e majority carrier
-h minority carrier
P-Type
-doped with trivalent
impurities
-Acceptor impurities
-h majority carrier
-e minority carrier
19. • The ability to produce semiconductor material of very high purity is
important.
• Adding one part of impurity (of proper type) per million in a wafer of Silicon
material can change the material from relatively poor conductor to a good
conductor of electricity.
• The ability to change the characteristics of a material through this process is
called doping.
Doping
20. Doping
• Doping process
– Adding impurities into pure semiconductor material (Si @ Ge)
• Why need doping process?
– To produce two types of semiconductor material
• N-type
• P-type
• Higher dopant concentration = more carriers (electrons or holes)
21. N-Type
• To produce N-type semiconductor
• The addition of pentavalent (5) or donor impurities contributes free electrons & greatly increasing
the conductivity of the intrinsic semiconductor.
+
Si
Antimony
Arsenic
Phosphorus
22. P-Type
• To produce P-type semiconductor
– The addition of trivalent (3) or acceptor impurities creates deficiencies of valence electrons,
called "holes"
Boron
Aluminium
Gallium
+
Therefore, creates a hole in the structure and it is considered the
MAJORITY carriers and the electrons are the MINORITY carriers.
Si
23. P-N Junction
• When p-type and n-types materials are placed in contact with
each other, the junction behaves very differently than either type
of material alone.
• The open circles on the left side of the junction above represent
"holes" which can act like positive charge carriers.
• The solid circles on the right of the junction represent the
available electrons from the n-type dopant.
24. P-N Junction
• Depletion region
– Electron and holes diffuses across the p-n junction creating depletion region
26. Depletion Region Process
• When a p-n junction is formed, some of the free electrons in the n-region
diffuse across the junction and combine with holes to form negative ions. In
doing so they leave behind positive ions at the donor impurity sites.
27. Depletion Region Process
• Filling a hole makes a negative ion and leaves behind a positive ion on the n-
side. A space charge builds up, creating a depletion region which inhibits any
further electron transfer unless it is helped by putting a bias or supply on the
junction.
29. Doped semiconductor material application: DIODE
• A diode is a circuit component, which is used to allow current flow through a
circuit in one way and blocking current from opposite direction.
30. How diode is formed?
• The combination of P and N doped semiconductor materials
31. • Formed by principle of doping semiconductor materials (such as
silicon) to create P and N-type semiconductors.
• When a P-type material and an N-type material are placed in close
contact, a PN junction is formed.
• This separation of charges develops a potential across the
depletion region, preventing further diffusion of carriers across
the junction.
• This potential, known as the potential barrier, is about 0.7V in a
typical silicon and 0.3V in a germanium p-n junction
How diode is formed?
32. Activity
1) The term 'covalent bonding' refers to:
(a) the introduction of an impurity
(b) the sharing of valence electrons
(c) the generation of surplus electrons
2) How many electrons are present in the outer valence shell of a silicon
atom?
(a) 1
(b) 2
(c) 4
3) In its pure state, silicon has the properties of:
(a) a conductor
(b) an insulator
(c) a semiconductor
4) In a semiconductor diode, the depletion region is removed when:
(a) the diode is in its forward conducting state
(b) the diode is in its reverse non-conducting state
(c) there is no potential difference between the anode and cathode
5) In a semiconductor, are the valence shells filled, empty, or partially filled?
6) Are electrons in the valence band of a semiconductor are in the bonding or anti bonding state?
7) As one electron is promoted from the valence band to the conduction band, a is formed in the valence band.
8) As the temperature increases, (more, less) electrons can be promoted to the conduction band?
9) Both and are considered charge carriers.
10) Group elements are used as dopants to produce n-type semiconductors, because they have than the
original Group 4 material.
11) Group elements are used as dopants to produce p-type semiconductors, because they have than the
original Group 4 material.
12) A diode contains both and regions.
13) For current to flow through a diode, the positive terminal of the power supply must be connected to the material.