This document discusses semiconductors and their properties. It explains that semiconductors have a small forbidden band gap that allows electrons to move between the valence and conduction bands with small amounts of energy. Semiconducting elements like silicon and germanium are used to form transistors and other electronic devices. Their conductivity increases when doped with small amounts of impurities to create either excess electrons (n-type) or holes (p-type). A p-n junction is formed by joining a p-type and n-type semiconductor, which acts as a rectifier that only allows current to flow in one direction.
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Semiconductor —I
Semiconductor —II
Semiconductor —III
N-Type Silicon
P-Type Silicon —I
P-Type Silicon —II
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the
boron atom filling the hole in boron atom and creating a “new”
hole in the silicon atom.
• It appears as though a hole moves toward the negative
terminal!Diode
•A diode is a 2 lead semiconductor that acts as a one way gate to electron flow.
– Diode allows current to pass in only one direction.
•A pn-junction diode is formed by joining together n-type and p-type silicon.
•In practice, as the n-type Si crystal is being grown, the process is abruptly altered to
grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined
crystal.
•The p-side is called anode and the n-side is called cathode.
•When the anode and cathode of a pn-junction diode are connected to external voltage
such that the potential at anode is higher than the potential at cathode, the diode is said
to be forward biased.
–In a forward-biased diode current is allowed to flow through the device.
•When potential at anode is smaller than the potential at cathode, the diode is said to
be reverse biased. In a reverse-biased diode current is blocked.
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Semiconductor —I
Semiconductor —II
Semiconductor —III
N-Type Silicon
P-Type Silicon —I
P-Type Silicon —II
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the
boron atom filling the hole in boron atom and creating a “new”
hole in the silicon atom.
• It appears as though a hole moves toward the negative
terminal!Diode
•A diode is a 2 lead semiconductor that acts as a one way gate to electron flow.
– Diode allows current to pass in only one direction.
•A pn-junction diode is formed by joining together n-type and p-type silicon.
•In practice, as the n-type Si crystal is being grown, the process is abruptly altered to
grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined
crystal.
•The p-side is called anode and the n-side is called cathode.
•When the anode and cathode of a pn-junction diode are connected to external voltage
such that the potential at anode is higher than the potential at cathode, the diode is said
to be forward biased.
–In a forward-biased diode current is allowed to flow through the device.
•When potential at anode is smaller than the potential at cathode, the diode is said to
be reverse biased. In a reverse-biased diode current is blocked.
Boudoir photography, a genre that captures intimate and sensual images of individuals, has experienced significant transformation over the years, particularly in New York City (NYC). Known for its diversity and vibrant arts scene, NYC has been a hub for the evolution of various art forms, including boudoir photography. This article delves into the historical background, cultural significance, technological advancements, and the contemporary landscape of boudoir photography in NYC.
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Fashionista Chic Couture Maze & Coloring Adventures is a coloring and activity book filled with many maze games and coloring activities designed to delight and engage young fashion enthusiasts. Each page offers a unique blend of fashion-themed mazes and stylish illustrations to color, inspiring creativity and problem-solving skills in children.
This document announces the winners of the 2024 Youth Poster Contest organized by MATFORCE. It lists the grand prize and age category winners for grades K-6, 7-12, and individual age groups from 5 years old to 18 years old.
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2. SEMI CONDUCTORS
DONE BY :
DILEEP KUMAR .D
HAREESH KUMAR .M
RAVI TEJA .G
UPENDRA .M
VENKATA SAI KUMAR
.D
3. Energy Band
■ In any material, there are 2 energy band:
1. Valence band : the outermost shell that determines the conductivity
2. Conduction band : the band outside the valence shell.
The 2 bands are separated by one energy gap called – forbidden gap.
■ The valence band contains with electrons.
■ The electrons can move to the conduction band if it have enough
energy ( eg: light or heat).
■ When the electron absorbs enough energy to jump from valence
band to the conduction band, the electron is said to be in excited
state.
4. ■ The concept of energy bands is particularly important in classifying materials
as conductors, semiconductors, and insulators.
• Semiconductor : has a smaller forbidden band and requires less energy to
move an electron from the valence band to the conduction band.
•Therefore, for a certain amount of applied voltage, more current will flow in the
semiconductor than in the insulator.
5. ■ semiconducting elements:
– low electrical conductivity at room temperature
– Electrical conductivity increases with temp.
■ Gap between valence and conduction band is intermediate in size.
■Semiconducting elements form the basis of solid state electronic
devices.
■Metalloids (such as silicon or germanium) are semiconducting
elements whose electrical conductivity increases as temperature
increases.
■A striking property of these elements is that their conductivities
increase markedly when they are doped with small quantities of other
elements.
6. ■ Made from materials that have four valence electrons in
their outer orbitals.
■ Germanium and silicon are the most common.
■ Silicon is preferred due to its ability to withstand heat.
■ A pure semiconductor material such as silicon or
germanium has no special properties and will make a
poor conductive material.
7. ■When silicon is doped with phosphorus, it becomes an n-type
semiconductor, in which electrical current is carried by negatively
charged electrons.
■When silicon is doped with boron, it becomes a p-type
semiconductor, in which an electrical current is carried by positively
charged holes.
■Joining a p-type semiconductor to an n-type semiconductor produces
a p-n junction, which can function as a rectifier.
■A rectifier is a device that allows current to flow in one direction, but
not the other.
8. :Types of
Semiconductor
■ Semiconductors are mainly classified into two
categories:
i. Intrinsic
ii. Extrinsic
i. Intrinsic : chemically very pure and possesses
poor conductivity.
-It has equal numbers of negative
carriers (electrons) and positive
carriers (holes).
- Impurities do not affect its electrical
behavior.
9. Intrinsic Semiconductor
Silicon has 4 outer shell
valence electrons
Forms into a lattice
structure to share electrons
The pure semiconductor material without impurities atoms.
example: Silicon and Germanium
10. Extrinsic
semicondu
ctor :
■ improved intrinsic semiconductor with a small
amount of impurities added by a process, known
as doping process, which alters the electrical
properties of the semiconductor and improves its
conductivity.
■ Introducing impurities into the semiconductor
materials (doping process) can control their
conductivity.
11. ■Adding impurities atom into intrinsic
semiconductor = extrinsic semiconductor.
■The process of adding specific types of
atoms to a semiconductor to favorably alter
electric characteristics – Doping
■2 types of extrinsic (impure)
semiconductor;
❖ N-type
❖ P-type
12. ■When an impurity increases the number of
free electrons, the doped semiconductor is
negative or n-type.
■An impurity that reduces the number of free
electrons, causing more holes, creates a
positive or p-type semiconductor.
13. Doping
■Doping : Adding impurities to the silicon
crystal lattice to increase the number of
carriers.
■Add a small number of atoms to increase
either the number of electrons or holes.
14. Donors n-Type Material
Donors
-Add atoms with 5 valence-band
electrons
-ex. Phosphorous (P)
-“Donates” an extra e- that can
freely travel around
-Leaves behind a positively
charged nucleus (cannot move)
-Overall, the crystal is still
electrically neutral
-Called “n-type” material
negative carriers)
(added
+
15. N– type material
Antimony (Sb) impurity in n-type material
- Diffused impurities with
5 valence electrons are
called donor atoms.
16. Acceptors Make p-Type Material
–
–
h+
Acceptors
• Add atoms with only 3 valence-
band electrons
• ex. Boron (B)
• “Accepts” e– and provides extra
h+
to freely travel around
• Leaves behind a negatively
charged nucleus (cannot move)
• Overall, the crystal is still
electrically neutral
• Called “p-type” silicon (added
positive carriers)
17. P-type material
Boron (B) impurity in p-type material
-
The diffused impurities
with 3 valence electrons
are called acceptor
atoms
18. PN Junction Formation
■
■
■
■ A PN junction is fabricated from a single slice of
semiconductor.
One side doped with acceptor impurity atoms – p region
One side doped with donor impurity atoms – n region
The interface separating the n and p regions is referred
as the metallurgical junction.
The PN junction
20. Semiconductor Properties
For T > 0K
Electron shaken free and can
cause current to flow
e–
h+
-Generation – Creation of an electron (e-)
and hole (h+) pair.
-h+ is simply a missing electron, which
leaves an excess positive charge (due to
an extra proton).
-Recombination – if an e- and an h+ come
in contact, they annihilate each other
-Electrons and holes are called “carriers”.
because they are charged particles – when
they move, they carry current.
-Therefore, semiconductors can conduct
electricity for T > 0K … but not much
current (at room temperature (300K), pure
silicon has only 1 free electron per 3 trillion
atoms).