1. The document discusses optical properties of semiconductors when exposed to electromagnetic radiation like light. 2. It explains concepts like absorption, reflection, transmission and emission spectra that can be obtained from materials and how they provide information about electronic band structures. 3. Key optical phenomena discussed include photon absorption promoting electrons from the valence to conduction band if the photon energy exceeds the semiconductor bandgap, and the interaction of light with materials leading to processes like reflection, refraction, scattering and dispersion.

1. Introduction to Optical Properties

3. • Recall: Semiconductor Bandgaps Eg are
usually in the range: 0 < Eg< 3 eV
(up to 6 eV if diamond is included)
• Also, at equilibrium, at temperature T = 0,
the valence band is full & the
conduction band is empty.
• Now, consider what happens if electromagnetic
radiation (“light”) is shined on the material.
• In the photon representation of this radiation
If hν ≥ Eg, some electrons can be promoted
to the conduction band leaving some holes in
the valence band.

4. • Now, consider some of the various possible types of
spectra associated with this process:
Absorption
Looks at the number of absorbed photons (intensity) vs.
photon frequency ω
Reflection
Looks at the number of reflected photons (intensity) vs.
photon frequency ω
Transmission
Looks at the number of transmitted photons (intensity)
vs. photon frequency ω
Emission
Looks at the number of emitted photons (intensity) vs.
photon frequency ω

5. • A (non-comprehensive) list of
Various Spectra Types:
Absorption, Reflection,
Transmission, Emission
• Each of these types of spectra is
very rich, complicated, & varied!
• Understanding such spectra gives
huge amounts of information about:
electronic energy bands, vibrational
properties, defects, …

6. 1. Refraction
2. Transmission
3. Reflection
a. Specular
b. Total internal
c. Diffused
4. Scattering
There is also
Dispersion
where different colors
bend differently
1. Refraction
2. Transmission
3. Reflection
a. Specular
b. Total internal
c. Diffused
4. Scattering
There is also
Dispersion
where different colors
bend differently
4
1
3b
2
3a
3c
Incident
light
“Semi-
transparent”
material
Interaction Between Light & Bulk Material
Many different possible processes can occur!

8. A Quick Review of “Light” & Photons
History: Newton & Huygens on Light
• Light as waves
• Light as particles
Christiaan Huygens
Isaac Newton
TheyThey stronglystrongly
disagreeddisagreed withwith
each other!each other!

9. Light – Einstein & Planck
• 1905 Einstein – Related the wave & particle
properties of light when he looked at the
Photoelectric Effect.
• Planck – Solved the “black body” radiation
problem by making the (first ever!) quantum
hypothesis: Light is quantized into quanta
(photons) of energy
E = hν. Wave-Particle duality.
(waves)
• Light is emitted in multiples of a certain minimum
energy unit. The size of the unit – the photon.
• Explains how an electron can be emitted if light
is shined on a metal
• The energy of the light is not spread but propagates
like particles .
(particles)

10. Photons
• When dealing with events on the atomic scale, it is often
best to regard light as composed of quasi- particles:
PHOTONS
Photons are Quanta of light
Electromagnetic radiation is quantized
& occurs in finite "bundles" of energy ≡
Photons
• The energy of a single photon in terms of its
frequency ν, or wavelength λ is,
Eph= hν = (hc)/λ

11. Maxwell – Electromagnetic Waves

12. • Light as an electromagnetic wave is characterized by a
combination of a time-varying electric field (E) & a
time-varying magnetic field (H) propagating through space.
• Maxwell’s Equations give the result that E & H satisfy
the same wave equation:
Changes in the fields
propagate through free space with speed c.
( ) ( )H,
tc
1
H, 2
2
2
2
ξ





δ
δ
=ξ∇
Light as an Electromagnetic Wave
(E, H)
∂2
∂
(E, H)

13. Speed of Light, c
• The frequency of oscillation,ν of the fields & their
wavelength, λoin vacuum are related by: c = νλo
• In any other medium the speed, v is given by: v = c/n = νλ
n ≡ refractive index of the medium
λ ≡ wavelength in the medium
µr
≡ relative magnetic permeability of the medium
εr
≡ relative electric permittivity of the medium
rrn εµ=
The speed of light in a medium is related to the
electric & magnetic properties of the medium. The
speed of light c, in vacuum, can be expressed as

14. The Electromagnetic Spectrum
Shorter
Wavelengths
Longer
Wavelengths
Increasing
Photon
Energy (eV)
Color & Energy
Violet ~ 3.17eV
Blue ~ 2.73eV
Green ~ 2.52eV
Yellow ~ 2.15eV
Orange ~ 2.08eV
Red ~ 1.62eV

15. Visible Light
• Light that can be detected by the human eye has
wavelengths in the range λ ~ 450nm to 650nm
& is called visible light:
• The human eye can detect light of many different colors.
• Each color is detected with different efficiency.
3.1eV 1.8eV
Spectral Response of Human Eyes
Efficiency,100%
400nm 600nm 700nm500nm

16. Visual Appearance of
Insulators, Metals, & Semiconductors• A material’s appearance & color depend on the interaction
between light with the electron configuration of the material.
Normally
High resistivity materials (Insulators) are Transparent
High conductivity materials (Metals) have a “Metallic
Luster” & are Opaque
Semiconductors can be opaque or transparent
This & their color depend on the material band gap
• For semiconductors the energy band diagram can explain
the appearance of the material in terms of both luster &
color.

17. Question
Why is Silicon Black & Shiny?

18. To Answer This:
• We need to know that the energy gap of Si is:
Egap = 1.2eV
• We also need to know that, for visible light, the
photon energy is in the range:
Evis ~ 1.8 – 3.1eV
So, for Silicon, Evis is larger than Egap
• So, all visible light will be absorbed & Silicon appears black
So, why is Si shiny?
• The answer is somewhat subtle: Significant photon
absorption occurs in silicon, because there are a significant
number of electrons in the conduction band. These
electrons are delocalized. They scatter photons.

19. Why is Glass Transparent?
• Glass is an insulator (with a huge band gap). Its is difficult
for electrons to jump across a big energy gap: Egap >> 5eV
Egap >> E(visible light) ~ 2.7- 1.6eV
• All colored photons are transmitted, with no absorption, hence the
light is transmitted & the material is transparent.
• Define transmission & absorption by
Lambert’s Law: I = Ioexp(-αx)
Io = incident beam intensity, I = transmitted beam intensity
x = distance of light penetration into material from a surface
α ≡ total linear absorption coefficient (m-1
)
α takes into account the loss of intensity from scattering
centers & absorption centers. α approaches zero for a
pure insulator.

20. What happens during the photon
absorption process?
Photons interact with the lattice
Photons interact with defects
Photons interact with
valence electrons
Photons interact with …..

21. The Concept of Effective Mass :The Concept of Effective Mass :
ComparingComparing
Free e-
in vacuum
An e-
in a crystal
In an electric field
mo =9.1 x 10-31
Free electron mass
In an electric field
In a crystal
m = ?
m*
effective mass
 If the same magnitude of electric field is applied
to both electrons in vacuum and inside the
crystal, the electrons will accelerate at a different
rate from each other due to the existence of
different potentials inside the crystal.
 The electron inside the crystal has to try to make
its own way.
 So the electrons inside the crystal will have a
different mass than that of the electron in
vacuum.
 This altered mass is called as an effective-effective-
mass.mass.

22. What is the expression forWhat is the expression for mm**
 Particles of electrons and holes behave as a wave under certain
conditions. So one has to consider the de Broglie wavelength to link
partical behaviour with wave behaviour.
 Partical such as electrons and waves can be diffracted from the
crystal just as X-rays .
 Certain electron momentum is not allowed by the crystal lattice. This
is the origin of the energy band gaps.
θλ sin2dn =
n = the order of the diffraction
λ = the wavelength of the X-ray
d = the distance between planes
θ = the incident angle of the X-ray beam

23. The energy of the free e-
is related to the k
free e-
mass , m0
is the propogation constant
dn 2=λ
k
π
λ
2
=
The waves are standing waves
The momentum is
kP =
(1)
(2)
By means of equations (1) and (2)
certain e-
momenta are not allowed
by the crystal. The velocity of the
electron at these momentum values
is zero.
The energy of the free electron
can be related to its momentum
m
E
P
2
2
= λ
h
P =
2
1
2 2 (2 )
22 2
2 2
2 2
E
m
kh hE
m m
k
λ π
=
= =

π2
h
=
momentum
k
Energy
E versus k diagram is a parabola.
Energy is continuous with k, i,e, all
energy (momentum) values are allowed.
E versus k diagram
or
Energy versus momentum diagrams

24. To find effective mass , mm**
We will take the derivative of energyenergy with respect to k ;k ;
2
2 2
2
2 2
2
*
dE k
dk m
d E
mdk
m
d E dk
=
=
=



Change m*m* instead of mm
This formula is the effective masseffective mass of
an electron inside the crystal.
- m*m* is determined by the curvature of the E-k curve
- m*m* is inversely proportional to the curvature

25. Direct an indirect-band gap materials :
 For a direct-band gap materialdirect-band gap material, the
minimum of the conduction band and
maximum of the valance band lies at the
same momentum, k, values.
 When an electron sitting at the bottom of
the CB recombines with a hole sitting at
the top of the VB, there will be no change
in momentum values.
 Energy is conserved by means of emitting
a photon, such transitions are called as
radiative transitions.
Direct-band gap s/c’s (e.g. GaAs, InP, AlGaAs)
+
e-
VB
CB
E
k

26.  For an indirect-band gap material; the
minimum of the CB and maximum of
the VB lie at different k-values.
 When an e-
and hole recombine in an
indirect-band gap s/c, phonons must
be involved to conserve momentum.
Indirect-band gap s/c’s (e.g. Si and Ge)
+
VB
CB
E
k
e-
PhononPhonon
 Atoms vibrate about their mean
position at a finite temperature.These
vibrations produce vibrational waves
inside the crystal.
 Phonons are the quanta of these
vibrational waves. Phonons travel with
a velocity of sound .
 Their wavelength is determined by the
crystal lattice constant. Phonons can
only exist inside the crystal.
Eg

27. Positive and negative effective mass
 The sign of the effective mass is determined
directly from the sign of the curvature of the E-k
curve.
 The curvature of a graph at a minimum point is a
positive quantity and the curvature of a graph at a
maximum point is a negative quantity.
 Particles(electrons) sitting near the minimum
have a positive effective mass.
 Particles(holes) sitting near the valence band
maximum have a negative effective mass.
 A negative effective mass implies that a particle
will go ‘the wrong way’ when an extrernal force
is applied.
Direct-band gap s/c’s (e.g. GaAs, InP, AlGaAs)
+
e-
VB
CB
E
k
2 2
2
*m
d E dk
=


28. -1
-2
0
2
3
1
4
GaAs
Conduction
band
Valance
band
0
ΔE=0.31
Eg
[111] [100] k
Energy(eV)
-1
-2
0
2
3
1
4
Si
Conduction
band
Valance
band
0
Eg
[111] [100] k
Energy(eV)
Energy band structures of GaAsGaAs and SiSi

29. -1
-2
0
2
3
1
4
GaAs
Conduction
band
Valance
band
0
ΔE=0.31
Eg
[111] [100] k
Energy(eV)
Energy band structure of GaAsGaAs
Band gap is the smallest energy
separation between the valence
and conduction band edges.
The smallest energy difference
occurs at the same momentum
value
Direct band gap semiconductor

30. Absorption Processes in Semiconductors
Important region:
Absorptioncoefficient(α,cm-1
)
Photon Energy (eV)
Absorption spectrum of a semiconductor.
Vis
Eg ~ Evis
Wavelength (µm)
IRUV
Lllllllllllllllllllllllllllllllllllllllllllllllllllllllllll lllllllllllllllllll

31. Absorption
An Important Phenomena in the Description of
the Optical Properties of Semiconductors
• Light (electromagnetic radiation) interacts with
the electronic structure of the material.
The Initial Interaction is Absorption
• This occurs because valence electrons on the
surface of a material absorb the photon energy &
move to higher-energy states.
• The degree of absorption depends, among
many other things, on the number of valence
electrons capable of receiving the photon
energy.

32. • The photon-electron interaction process
obviously depends strongly on the photon energy.
• Lower Energy Photons interact principally by
ionization or excitation of the solid’s valence electrons.
• Low Energy Photons (< 10 eV) are in the infrared
(IR), visible & ultraviolet (UV) in the EM spectrum.
• High Energy Photons (> 104
eV) are in the X-Ray
& Gamma Ray region of the EM spectrum.
• The minimum photon energy to excite and/or
ionize a solid’s valence electrons is called the
Absorption Edge or

33. Valence Band – Conduction Band Absorption
(Band to Band Absorption)
Conduction Band, EC
Valence Band, EV
Egap
hν = Ephoton

34. Conduction Band, EC
Valence Band, EV
Egap
hν = Ephoton
This process obviously requires that the minimum energy of a
photon to initiate an electron transition must satisfy
EC - EV = hν = Egap
Valence Band – Conduction Band Absorption
(Band to Band Absorption)

35. Valence Band – Conduction Band Absorption
(Band to Band Absorption)
Conduction Band, EC
Valence Band, EV
Egap
hν = Ephoton
This process obviously requires that the minimum energy of a
photon to initiate an electron transition must satisfy
EC - EV = hν = Egap
If hν > Egap then
obviously a transition
can happen. Electrons
are then excited to the
conduction band.

36. Direct Band Gap Absorption
K (wave number)
hν
Conservation of Energy
hν = EC(min) - Ev (max) = Egap
Conservation of
Momentum
Kvmax + qphoton = kc
E
A Direct Vertical
Transition!
The Photon
Momentum
is Negligible

37. Indirect Band Gap Absorption
E
K (wave number) hν

38. Some of the many applications
– Emission:
light emitting diodes (LED) & Laser Diodes (LD)
– Absorption:
– Filtering: Sunglasses, ..
Si filters (transmission of infra red light with simultaneous
blocking of visible light)

39. • If there are many impurity levels the photons with
energies smaller than the band gap energy can be
absorbed, by exciting electrons or holes from these
energy levels into the conduction or valence band,
respectively
– Example: Colored Diamonds

40. Light, when it
travels in a
medium can be
absorbed and
reemitted by every
atom in its path.
Refraction, Reflection &Dispersion
Defined by refractive index; n
Small n
High n
n1 = refractive index of
material 1
n2 = refractive index of
material 2

41. Nanostructured materialsNanostructured materials
• 0D: quantum dots0D: quantum dots
• 1D: Nanowires1D: Nanowires
• 2D: superlattices and heterostructures2D: superlattices and heterostructures
•

42. Nanostructured materials derive their special properties from
having one or more dimensions made small compared to a
length scale critical to the physics of the process.
      
   

43. Electronic DOS and dimensionalityElectronic DOS and dimensionality
Size effects are most
evident at band edges
(semiconductor NPs).
DOS (dn/dE) as
a function of
dimensionality.
3D case is for
free particles.
Copyright Stuart Lindsay 2009

44. 0D Electronic Structures:0D Electronic Structures:
Quantum DotsQuantum Dots
Light incident on a semiconductor at an energy greater than theLight incident on a semiconductor at an energy greater than the
bandgap forms an exciton, i.e. an electron-hole quasiparticle,bandgap forms an exciton, i.e. an electron-hole quasiparticle,
representing a bound state.representing a bound state.

45. Quantum Dots (QD)
 Semiconductor nanostructures
 Size: ~2-10 nm or ~10-50 atoms
in diameter
 Unique tunability
 Motion of electrons + holes = excitons
 Confinement of motion can be created by:
 Electrostatic potential
 e.g. in e.g. doping, strain, impurities,
external electrodes
 the presence of an interface between different
semiconductor materials
 e.g. in the case of self-assembled QDs
 the presence of the semiconductor surface
 e.g. in the case of a semiconductor nanocrystal
 or by a combination of these

46. Quantum Confinement Effect
 E = Eq1
+ Eq2
+ Eq3,
Eqn
= h2
(q1
π/dn
)2
/ 2mc

47. QD – Fabrication Techniques
 Core shell quantum
structures
 Self-assembled QDs
and Stranski-
Krastanov growth
 MBE (molecular beam
epitaxy)
 MOVPE
(metalorganics vapor
phase epitaxy)
 Monolayer fluctuations
 Gases in remotely
doped
heterostructures
Schematic representation of different approaches to
fabrication of nanostructures: (a) microcrystallites in
glass, (b) artificial patterning of thin film structures,
(c) self-organized growth of nanostructures

48. QDL – Predicted Advantages
 Wavelength of light determined by the energy levels not by
bandgap energy:
 improved performance & increased flexibility to adjust the
wavelength
 Maximum material gain and differential gain
 Small volume:
 low power high frequency operation
 large modulation bandwidth
 small dynamic chirp
 small linewidth enhancement factor
 low threshold current
 Superior temperature stability of I threshold
I threshold
(T) = I threshold
(Tref
).exp ((T-(Tref
))/ (T0
))
 High T0
 decoupling electron-phonon interaction by increasing the
intersubband separation.
 Undiminished room-temperature performance without external thermal
stabilization
 Suppressed diffusion of non-equilibrium carriers  Reduced
leakage

49. QDL – Basic characteristics
 An active medium to
create population
inversion by pumping
mechanism:
 photons at some site
stimulate emission at
other sites while
traveling
 Two reflectors:
 to reflect the light in
phase
 multipass amplification
Components of a laser
 An energy pump source
 electric power supply

50. QDL – Basic characteristics
 An ideal QDL consists of a 3D-array of dots with
equal size and shape
 Surrounded by a higher band-gap material
 confines the injected carriers.
 Embedded in an optical waveguide
 Consists lower and upper cladding layers (n-doped
and p-doped shields)

51. Quantum Lasers,
M. Momeni
51
Single-Quantum Well Laser (SQWL)
Double
Heterostructure:
GFpFn EEE >−
)(1)( VVVC EfhfEf −>+ or,
alternatively,
Basic Laser
condition:
nm
hf
V > 0
P p N
EV
EC
EFpEFn
Eel
Ehole

52. Quantum Lasers,
M. Momeni
52
Multiple-Quantum Well Laser (MQWL)
P p P
EV
EC
MQW using isotype SQW:
mini
bands
P p P p P p P p P
hf hf hf hf
MQW DFB
MQW DFB

53. Photodiode

54. Basic principle for Optical Detection
• A photodiode is a type of photodetector capable of
converting light into either current or voltage, depending
upon the mode of operation
• A p-n photodiode is generally reversed biased
• Due to this reversing biasing,a thick depletetion layer
develops on either side of the junction.
• The large potential barrier has the effect of preventing
the majority carriers of both the regions crossing the
junction in the opposite direction to the field due to the
barrier potential.

55. When a photon of light is incident in or near the
depletetion region and if the energy of the photon is
equal or greater than the bandgap energy (Eg) of the
semiconductor material of the p-n junction , the
photon will excite an electron in the valance band
(V.B) to the conduction band (CB) and this process
will generate an “ electron-hole” pair.

56. The photo-generated carriers are separated in the
depletetion layer and are swept away by the electric field to
due to the reverse bias voltage and a leakage current flows
in the external circuit.
The width of the depletetion layer must be sufficiently thick
so as to allow large portion of the the incident light to
be absorbed and thus
the maximum current
pair generation is obtained

57. Optoelectronicsp-n Junction Photodiode
p-i-n Photodiode
Avalanche Photodiode

58. Function and principle
 The function of photodiode is conversion of light
signal to an electrical signal.
 This is achieved by the creation of free electron hole
pairs (EHPs) by the absorption of photons, that is, the
creation of electrons in the conduction band and
holes in the valence band.

59. .
Fig 3- a)A schematic diagram of a reverse biased pn junction photodiode.
b)Net space charge density across the diode in the depletion region.
c)The electric field in the depletion region.

60. PN JUNCTION PHOTODIODE
 The photodiode consists of a p+ type thin layer
deposited on an n type substrate and light enters into its
p-type region.
When the diode is reversed biased larger portion of the
depletetion region occupies the n region around the
junction due to smaller impurity concentration.
the photons of light enter the depletetion region to
produce the electron hole pairs.The electrons are
attracted by the positive terminal while the holes are
drawn by the negative terminal of the applied reverse
bias voltage.

61. Figures from Wikipedia
AFM COMPONENTSfeedback

62. Sourav Sarkar
Asst Professor
Dept of ECE
SIT

63. • Discovered in 1879 by Edwin H. Hall and
published in the paper "On a New Action of
the Magnet on Electrical Current"
• Noticed that a when a magnetic field was
applied to a current-carrying thin metal strip,
a small transverse voltage appeared
• Provides a simple method for accurately
measuring carrier density, electrical
resistivity, and the mobility of carriers in
semiconductors

64. Basic Physical Phenomena
• When an electron moves in a direction perpendicular to an applied magnetic
field, it experiences a force (Lorentz force) acting normal to both directions
and moves in response to this force (see below for an n-type semiconductor)
B
V=0
V-VH
xv
y
B
F
z
Coordinate
System
Lorentz Force
F=-ev x B
d
I
e-
– Constant current I (flows along
x-axis) in the presence of
magnetic field B (z-axis) causes
Lorentz force F (y-axis)
– Causes electron paths to bend
towards negative y-axis
– Charge builds up on the surface
of the side of sample, and the
potential drop across the two
sides of the sample is known as
the Hall voltage (VH)

65. Standard Hall Effect Experiment
 Current from the
applied E-field
Lorentz force from the magnetic field
on a moving electron or hole
e- v
Top view—electrons
drift from back to front
e+ v
E field
e-
leaves + & – charge on
the back & front surfaces–
  Hall Voltage
The sign is reversed for
holes

66. Electrons flowing without a magnetic fieldElectrons flowing without a magnetic field
t
d
semiconductor slice
+ _
I I

67. When the magnetic field is turned on ..When the magnetic field is turned on ..
B-field
I qBv

68. As time goes by...As time goes by...
I
qBv = qE
low
potential
high
potential
qE

69. Finally...Finally...
B-field
I
VH

70. Phys 320 - Baski Solid-State Physics
• Why is the Hall Effect useful? It can determine the
carrier type (electron vs. hole) & the carrier density n for a
semiconductor.
• How? Place the semiconductor into external B field,
push current along one axis, & measure the induced Hall
voltage VH along the perpendicular axis. The following
can be derived:
• Derived from the Lorentz force FE = qE = FB = (qvB).
n = [(IB)/(qwVH)]
Semiconductors: Charge Carrier Density via Hall Effect
Hole Electron
+ charge – charge
BF qv B= ×
r rr

71. Reminder: The Lorentz Force
F = q[E + (v × B)]

72. qEy=qvxBz
…………………………..1.
y state the magnetic field force will be exactly balannced by the induced ele
Here vx = velocity and Bz = magnetic field
The induced electric field in the y direction is called hall Field.
The hall Field produce a
voltage across the semiconductor which is called hall voltage. We
can write
VH=+EH W = Ey W
…………………..2
From equation 2 and 1 we can write …
VH =vxBzW ……………3
For a p-type semiconductor , the drift velocity of holes can be written as
vdx = JX /ep = IX /(ep)(Wd) …….4
where e is the magnitude of electronics charge .Combining equation 3 and
we have
VH =IxBz/epd …………………………….5
solving for hole concentration , we obtain
p= IxBz/ed VHmajority carrier hole concentration is determined from the current , magneti
hall voltage

73. qEy=qvxBz
…………………………..1.
In Steady state the magnetic field force will be exactly balannced by the induced electric field
Here vx = velocity and Bz = magnetic field
The induced electric field in the y direction is called hall Field. The hall Field produce a
voltage across the semiconductor which is called hall voltage. We can write
VH=+EH W = Ey W …………………..2
From equation 2 and 1 we can write …
VH =vxBzW ……………3
For a p-type semiconductor , the drift velocity of holes can be written as
vdx = JX /ep = IX /(ep)(Wd) …….4
where e is the magnitude of electronics charge .Combining equation 3 and 4
we have
VH =IxBz/epd …………………………….5
solving for hole concentration , we obtain
p= IxBz/ed VH
The majority carrier hole concentration is determined from the current , magnetic field
and hall voltage

74. • The number of conduction electrons per unit volume (N) is found by:
Where Ix= current, Bz= magnetic field, d=sample thickness, e= elementary charge,
VH=Hall voltage in the y-direction
• The Hall Resistance, or Hall constant, (RH) is often defined:
• Thus, the Hall voltage (VH) can be written as:
• Then, the Hall mobility (µ) can be determined:
Where Rs is the sheet resistance, easily determined by the van der Pauw method
Important Equations
VH=
IxBz
Ned
=IxRH
Bz
d
µ=
VH
RsIxBz
=
1
RsNde
N=
IxBz
edVH
RH =
1
Ne

75. • Advantages:
– Simple, low-cost, fast turn-around
time
– High sensitivity: Can measure
carrier concentrations in doped
silicon of <1012
e-/cm3
Hall Measurement Strengths
• Usefulness:
– Resistance and conductance were used for characterization in the early
1800’s, but they are influenced by sample geometry and are not material
properties.
– For comparison between samples with different geometries, resistivity
and conductivity were used. However, they are still not material
properties.
– The Hall Effect allows measurement of carrier density and mobility,
which are material properties, giving a deeper level of understanding of
materials.

76. Technological Applications
• Industrial and commercial use:
– Electronics industry: Manufacturing low-noise transistors, electronic compasses
– Automobile Industry: Fuel injection systems and anti-lock brake systems
– Computers: Brushless DC rotors and disk-drive index sensors
– In general:
• Hydraulic controls
• Integration into magnetic shields to reduce stray fields
• Inspect tubing or pipelines for corrosion or pitting
References: 5, 6, 7.
• Hall Effect sensors for sensing position,
motion, magnetic fields fluid flow, power,
or pressure
– Long life (30 billion operations, in some tests)
– High speed operation (> 100 kHz possible)
– Highly repeatable operation
– Stationary operation (no moving parts)
– Compatible input/output for logic devices)
Hall effect current sensor.
Dimensions≈ 30x15x11mm.

77. Thank You