This document provides an overview of basic electronics topics related to semiconductors. It discusses semiconductors and their charge carriers, how temperature affects semiconductors, types of semiconductors including n-type and p-type, types of impurities used for doping, the p-n junction diode, diode characteristics, applications of diodes, and advantages of p-n junction diodes over thermionic diodes. It also lists lesson contents, modes of conduction in semiconductors, effects of temperature, classification of materials, and differences between intrinsic and extrinsic semiconductors. Examples and classwork questions are provided at the end.

1. BASIC ELECTR

2. BASIC ELECTRONICS
SS3PHY
 SEMICONDUCTORS
 CHARGE CARRIES IN SEMICONDUCTORS
 EFFECT OF TEMPERATURE ON
SEMICONDUCTOR
 TYPES OF SEMICONDUCTORS
 TYPES OF IMPURITIES
 THE P-n JUNCTION DIODE
 JUNCTION DIODE CHARACTERISTICS
 APPLICATION OF THE p-n JUNCTION DIODE
 ADVANTAGES OF THE p-n JUNCTION DIODE
OVER THE THERMIONIC DIODE.
LESSON CONTENTS

3. SS3PHY
SEMICONDUCTORS
These are materials whose electrical
conductivity is intermediate in value b/w
that of good Conductors and Insulators.
e.g. Si, Ge. Pure semiconductors are also
known as Intrinsic Semiconductor.
They are widely used in the electronic
industry (computer & telecommunication).
 They have crystalline structure.
 They are group four elements & have four
electrons in their outermost shell.

4. SS3PHY
Classification of Metals,
Conductors and Semiconductors
Base on relative values of electrical
conductivity (σ) and resistivity (ρ), solids
are broadly classified as;
(i) Metal: they posses high conductivity &
low resistivity.(ρ~10-2Ωm -10-8Ωm &
σ~102NM
- 10-3NM) ~
(i) Semiconductors: their resistivity &
conductivity are intermediate to metals

5. SS3PHY
MODE OF CONDUCTION OF
SEMICONDUCTORS
Semiconductors conductor electricity using two types
of charge carriers namely;
• Negatively-charged free electrons &
• Positively-charged holes.
• Free electrons & holes are created due to thermal
liberation of the valence electrons from their crystal
structure. They moved around randomly in different
direction inside the semiconductor.
• electron-hole pairs are created when valence
electrons are thermally liberated from the crystal
structure of the semiconductor.When semiconductor is

6. SS3PHY
MODE OF CONDUCTION OF
SEMICONDUCTORS
One way of increasing the conductivity of a
semiconductor is to increase it temperature. Given an
electron enough thermal energy, it breaks free from its
atomic bond & moves as a free electron. A hole of (+)
is created & by chance another free electron will falls
into the hole & loose its energy. The kind of moving of
free charge is how pure semiconductor conduct
electricity. This process forms a cycle of energy
transfer b/w free, bound electrons & holes. The
number of free electrons(n) is equal to the number of
holes p as to enable the atomic lattice remains

7. The electrical resistance of pure metals
increases with temperature rise.
It means pure metal conductivity decreases
with temperature rise.
 However, the electrical resistance of a pure
semiconductor decreases with temperature
rise.
 Hence, Pure semiconductor conductivity
increase with temperature rise.
This is a means to differentiate b/w pure metal
EFFECT OF TEMPERATURE ON
SEMICONDUCTOR

8. Basically there are
two types namely;
 n-type semiconductors
p-type semiconductors
TYPES OF SEMICONDUCTORS

9. n-type Semiconductors: They are
produced when introducing a tiny amount of
impurity to a pure semiconductor through a
process called doping. A deliberate addition of a
desirable impurity to a intrinsic semiconductor
as to increase its conductivity is called doping
.The negative charge carriers are the majority
while the positive charge carries are the
minority. Conduction is mainly by the majority.
An n-type semiconductor can be produces by
doping Ge With Arsenic or Antimony.
The doping result to more free electrons.
TYPES OF SEMICONDUCTORS

10. p-type Semiconductors: They
are produced by doping pure Ge or Si
with an impurity like Indium or Boron.
The Holes are the majority & the
positive charge carriers while the
electrons (negative charge carriers) are
the minority. Doping results into an
impure semiconductor with more holes
than electrons.
TYPES OF SEMICONDUCTORS

11. There are two types of
impurities namely;
 Donor Impurities
 Acceptor Impurities
TYPES OF IMPURITIES

12. Donor Impurities:
They are atoms of elements with
five (5) valance electrons whereby
after covalent bond with four
electrons of a pure semiconductor &
the remaining electron becomes a
conducting electron without a hole.
Donor impurities give rise to n-type
of semiconductor.
TYPES OF IMPURITIES

13. TYPES OF IMPURITIES

14. Acceptor Impurities:
They are atoms of elements with three
(3) outermost electrons whereby after
bonding with a pure semiconductor,
there is a vacancy.
The acceptor impurity increase the
number of holes without contributing
electrons. Acceptor impurities give rise
to p-type of semiconductor.
TYPES OF IMPURITIES

15. TYPES OF IMPURITIES

16. DIFFERNECS B/W INTRISIC &
EXTRINSIC SEMICONDUCTORS

17. THE N-P JUNCTION DIODE
When p & n-type semiconductors join to
act as a single semiconductor it is called a p-n
junction. The p-n junction function like a
thermionic diode. Semiconductor diodes are
two-terminal devices that consist of a p-n
junction and metallic contacts at their two ends.
Diode Symbol

18. THE N-P JUNCTION DIODE
(+) terminal to the p-type semiconductor.
(-) terminal to the n-type semiconductor.
It has low resistance & allows I flow easily.

19. THE n-p JUNCTION DIODE
(+) terminal to the n-type semiconductor.
(-) terminal to the p-type semiconductor.
It has high resistance & does not allow I flow

20. JUNCTION DIODE XTERISTICS
The xteristics graph is shown for both the forward
& reverse biases on the same axis when I is
plotted against V. The graph does not follow
ohm’s law since junction diode is a non-conductor

21.  Due to unique ability to conduct I in
one direction, it is used in rectifier
circuits.
 In communication circuits, they are used
as signal diodes.
 Rectification of alternating current.
 Photodiode works as photo-detector.
 Zener diode for stabilization of current
in electronic system
 Gunn diode as a component of high
APPLICATIONS OF P-N JUNCTION DIODE

22. o It is less liable to break.
o It is much smaller.
o Cheaper to produce in large
numbers.
o Needs small p.d. to operate in
a radio receiver.
o It requires no time to warm up
ADVANTAGES OF P-N JUNCTION
OVER THE TEHRMIONIC DIODE

23. The process of converting
a.c to d.c is called rectification.
A rectifier circuit is a circuit in
which an a.c. input voltage is
converted to a d.c. output
voltage. In a circuit, junction
diode makes it possible.
RECTIFICATION/RECTIFIER CIRCUITS

24. Ex1. Which of the following
statements about a diode is correct/ (A) reverse
bias diodes have low resistance (B) Forward
bias diodes have high resistance (C) Forward
bias diodes produce high current (D) Forward
bias diodes function as a result of heat.
Ex. Define doping.
Ex3. State five differences b/w extrinsic ans
intrinsic semiconductors
EXAMPLES
SS3PHYS

25. 1.State three ways that the
forward bais p-n junction is
different from the reverse bias
p-n junction.
2. Apart from Indium and
Aluminum state three other
group three elements for doping
CLASSWORK
SS3PHYS

26. SS3PHYS
1.Mention five types of semiconductor
dioses
2.Explain five advantages of p-n
junction diode over thermionic
diode.
3. What is a rectifier?
4. Explain five uses of semiconductor
diodes.
SUBJECT: PHYSICS
TOPIC: WBASIC ELECTRONICS
ASSIGNMENT N0. 8

27. THANK
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