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We always ask if there’s still
hope left or if there’s still time.
But we never realize that hope
only leaves when we doubt
and time only runs out
the moment we give up.
Solid State 3
Devices
• Operates by virtue of the
movement of electrons with
solid piece of semiconductor
material
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Electrical Classification of Materials
• Conductor
• Insulator
• Semiconductor
Conductor
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Conductor 6
• A material with LESS THAN 4
VALENCE ELECTRONS.
• Copper (Cu), Silver (Ag), Gold
(Au) and Aluminum (Al)
Insulator
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Materials Conductivity
• Silver 63.01 x 106 S/m
• Copper 59.60 x 106 S/m
• Gold 45.20 x 106 S/m
• Aluminum 37.80 x 106 S/m
• Iron 10.44 x 106 S/m
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Insulator
• A material with MORE THAN 4
VALENCE ELECTRONS.
• glass, mica, hard rubber
Semiconductor
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Semiconductor
• A material with EXACTLY 4 VALENCE
ELECTRONS.
• Semiconductors have electrical
characteristics in between conductors and
insulators.
• SILICON, GERMANIUM are examples of
semiconductor materials.
Energy Gap (Eg) Comparison
Energy Gap (Eg) Comparison
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Bonding of Atoms
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Energy Gaps
• Silicon 1.11 eV
• Germanium 0.67 eV
• Silicon Carbide 2.86 eV
• Aluminum Phosphide 2.45 eV
• Gallium Arsenide 1.43 eV
• Indium Phosphide 1.35 eV
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Bonding of Atoms
• Ionic Bond
• Metallic Bond
• Covalent Bond
Ionic Bond
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Ionic Bond
• Results from attractive forces
between positive and negative
ions or between pairs of
oppositely charged ions.
Metallic Bond
Metallic Bond
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• Results from attractive forces
between a group of positive
ions and a sea of electrons that
are free to move about among
its ions.
Covalent Bonding
Covalent Bonding
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• Results when atoms
SHARE THEIR
VALENCE ELECTRONS
with other atoms .
• The shared electrons
are attracted
simultaneously to two
atoms resulting in a
force that holds them
together.
Conduction in Semiconductors
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Conduction in Semiconductors
• Electron current flow
• Hole current flow
Electron Flow
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Electron Flow
Hole Flow
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Hole Flow
Types of Semiconductor materials
Types of Semiconductor Materials 20
• Intrinsic Material
• A Semiconductor that is FREE FROM
IMPURITIES, such as Silicon or Germanium.
• Extrinsic Materials
• Semiconductor materials with SOME IMPURITIES
ADDED to change its electrical properties.
• The process of adding impurities is called DOPING.
Type of Extrinsic Materials
Type of Extrinsic Materials 21
• N-TYPE SEMICONDUCTORS
• An extrinsic semiconductor material formed by adding DONOR
impurities, such as as PENTAVALENT atoms.
• Majority carriers are ELECTRONS
• Minority carriers are HOLES
Type of Extrinsic Material
Type of Extrinsic Material 22
• P-TYPE SEMICONDUCTORS
• An extrinsic semiconductor material formed by adding
ACCEPTOR impurities, such as TRIVALENT atoms.
• Majority carriers are HOLES
• Minority carriers are ELECTRONS
Types of Dopes
Types of Dopes 23
• DONOR or PENTAVALENT ATOMS
• N-TYPE
• PHOSPOROUS
• ANTIMONY
• ARSENIC
• BISMUTH
• ACCEPTOR or TRIVALENT ATOMS
• P-TYPE
• GALLIUM • ALUMINUM
• BORON • INDIUM
Semiconductor Diodes
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Semiconductor Diodes
The PN Junction
The PN Junction 25
• When the P-TYPE material and N-TYPE material
are BROUGHT TOGETHER, they form a so-called
PN JUNCTION.
Formation of Depletion Region
Formation of Depletion Region 26
• The region created by
the PN junction
forming a barrier
potential.
• The DEPLETION refers
to the fact that the
region near the PN
junction is DEPLETED
of CHARGED
CARRIERS due to
diffusion across the
junction.
Barrier Potential
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Barrier Potential
• The POTENTIAL
DIFFERENCE of the
electric field across the
depletion region is the
AMOUNT OF VOLTAGE
required to move
electrons through the
electric field.
• 0.7V for Silicon
• 0.3 for Germanium
• Barrier potential
DECREASES as
temperature INCREASES
Biasing the Diode
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Biasing the Diode
• BIAS refers to the use of a dc
voltage to establish a certain
operating condition for an electronic
device.
• Types:
• Forward Bias
• Reverse Bias
Forward Bias
Forward Bias
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• Is the condition
that ALLOWS
CURRENT
THROUGH THE PN
JUNCTION to flow
when a dc voltage
is applied to a PN
junction
Reverse Bias
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Reverse Bias
• Is the condition that
ESSENTIALLY PREVENTS
CURRENT through the
diode when a dc voltage
is applied to a PN
junction.
• MINORITY CARRIERS
• The EXTREMELY SMALL
CURRENT THAT EXIST IN
THE REVERSE BIAS
condition.
Breakdown Voltage
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Breakdown Voltage
• The MAXIMUM VOLTAGE the junction
diode can handle when reverse
biased.
• Also known as PEAK REVERSE
VOLTAGE (PRV) OR PEAK INVERSE
VOLTAGE (PIV)
Voltage-Current Characteristic of Diode
