1. S E M I C O N D U C T O R S
Created by-
BISHNUPADA SARKAR
XII-B, 17

2. INTRODUCTION
A semiconductor material has an electrical
conductivity value falling between that of
a conductor, such as metallic copper, and
an insulator, such as glass.
Its resistivity falls as its temperature rises;
metals are the opposite.
SILICON ORE

3. After silicon, gallium arsenide is the second
most common semiconductor and is used
in laser diodes, solar cells, microwave-
frequency integrated circuits and others.
Silicon is a critical element for fabricating
most electronic circuits

4. Its conducting properties may be altered
in useful ways by introducing impurities
("doping") into the crystal structure.
Some examples of semiconductors
are silicon, germanium, gallium arsenide,
and elements near the so-called
"metalloid staircase" on the periodic
table.

5. When two differently-doped regions exist in the
same crystal, a semiconductor junction is created
The behaviour of charge carriers, which
include electrons, ions and electron holes, at these
junctions is the basis of diodes, transistors and all
modern electronics

6. 
TYPES OF
SEMICONDUCTORS
 INTRINSIC SEMICONDUCTORS
 EXTRINSIC SEMICONDURS
 N TYPE
 P TYPE

7. 
INTRINSIC
SEMICONDUCTOR
An intrinsic(pure) semiconductor, also called
an un-doped semiconductor or i-type
semiconductor, is a pure semiconductor without
any significant dopant species present. The
number of charge carriers is therefore determined
by the properties of the material itself instead of
the amount of impurities. In intrinsic
semiconductors the number of excited electrons
and the number of holes are equal: n = p.

8. 
EXTRINSIC
SEMICONDUCTORS
Doped semiconductors are referred to
as extrinsic. By adding impurity to the
pure semiconductors, the electrical
conductivity may be varied by factors of
thousands or millions

9. 
N-TYPE
An electron donor dopant is an atom which,
when incorporated in the crystal, releases a
mobile conduction electron into the crystal
lattice. An extrinsic semiconductor which has
been doped with electron donor atoms is
called an n-type semiconductor, because the
majority of charge carriers in the crystal are
negative electrons

10. 
P-TYPE
An electron acceptor dopant is an atom which
accepts an electron from the lattice, creating a
vacancy where an electron should be called
a hole which can move through the crystal like a
positively charged particle. An extrinsic
semiconductor which has been doped with
electron acceptor atoms is called a p-type
semiconductor, because the majority of charge
carriers in the crystal are positive holes

11. 
BAND GAPS
the band gap generally refers to the energy
difference (in electron volts) between the top
of the valence band and the bottom of the
conduction
band in insulators and semiconductors. It is
the energy required to promote a valence
electron bound to an atom to become
a conduction electron,

12. which is free to move within the crystal lattice
and serve as a charge carrier to
conduct electric current.

13. 
A diode is a two-terminal electronic
component that conducts current primarily in
one direction (asymmetric conductance); it has
low (ideally zero) resistance in one direction,
and high (ideally infinite) resistance in the
other. A diode vacuum tube or thermionic
diode is a vacuum tube with two electrodes, a
heated cathode and a plate, in which electrons
can flow in only one direction, from cathode to
plate.
DIODES

14. A semiconductor diode, the most commonly
used type today, is a crystalline piece
of semiconductor material with a p–n
junction connected to two electrical
terminals. Semiconductor diodes were the
first semiconductor electronic devices. The
discovery of asymmetric electrical
conduction across the contact between a
crystalline mineral and a metal was made by
German physicist Ferdinand Braun in 1874.

15. Today, most diodes are made of silicon, but
other semiconducting materials such
as gallium arsenide and germanium are also
used.
DIODE

16. 
A transistor is a semiconductor device used
to amplify or switch electronic signals
and electrical power. It is composed
of semiconductor material usually with at least
three terminals for connection to an external
circuit. A voltage or current applied to one pair
of the transistor's terminals controls the current
through another pair of terminals.
TRANSISTORS

17. Because the controlled (output) power can be
higher than the controlling (input) power, a
transistor can amplify a signal. Today, some
transistors are packaged individually, but many
more are found embedded in integrated
circuits.
transistors

18. 
 Semiconductor devices have replaced vacuum
tubes in most applications. They use electrical
conduction in the solid state rather than the gaseous
state or thermionic emission in a vacuum.
APPLICATIONS

19.  Semiconductor materials are useful
because their behaviour can be easily
manipulated by the deliberate addition
of impurities, known as doping.
 Semiconductor conductivity can be
controlled by the introduction of an
electric or magnetic field, by exposure
to light or heat, or by the mechanical
deformation of a doped mono-crystalline
silicon grid; thus, semiconductors can
make excellent sensors.

20.  Current conduction in a
semiconductor occurs due to mobile
or "free" electrons and electron holes,
collectively known as charge
carriers.
Without transistors and integrated
circuits made of semiconductors,
much of modern life would be very
different.

21.  No hand-held electronic games
would entertain children for hours.

22. No bar-code readers would speed
checkout lines and compile
inventories at the same time.

23. And no computers would handle
tasks at work and home, nor would
microprocessors control the
operations of cars, planes, and space
vehicles.

24. 
CONCLUSION
The semiconductors have been boon to our technological
development, it has reduced the size of our gadgets and made
them more efficient.

25. !!