Electronic materials – basics, properties &
applications
IITD&M talk
Parasuraman S
Dept. of Metallurgical and Materials Engineering
IIT – Madras
Date: 24/10/14
1
Outline
• History of computers
• The age of Si
• Opto electronic devices
• Future technology
http://www.jantoo.com/cartoons/keywords/computer-graphics
2
Introduction clip
‘Chitti’ – the robot
• Speed – 1 THz – 1012 Hz
• Memory – 1 TB – 1012 Bytes
http://www.youtube.com/watch?v=NXx-draUTdA
3
Current fastest supercomputer
• Record for fastest supercomputer is Tianhe-2 or TH-2
• Developed in 2013
Specifications
• Memory: 1024000 GB (1015
Bytes)
• Processor: Intel Xeon E6-2692
2.2 GHz
• Cores: 31,20,000
• Peak performance: 54902.4
TFlops (1016 Flops) –floating
point calculations per second
National supercomputer center,
Guangzhou, China
http://top500.org/system/177999
http://www.top500.org/featured/systems/tianhe-2/
4
World’s first computer – ENIAC
• ENIAC – 1947 – 1955 (60 years ago)
• Processing speed
• 385 multiplications per second
• Basic cycle – 200 micro sec
http://en.wikipedia.org/wiki/ENIAC
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Vacuum tubes – diodes and triodes
• Early devices – vacuum
tubes – ENIAC
• Diode – rectifier –
conduct in one direction
• Triode
•
•
Diode
Switch – control grid –
turn on and off current
Amplifier – small input
signal – large output
signal
• Basic blocks – huge,
ineffective, expensive ,
and slow
Triode
Size reduction – make solid state devices
http://en.wikipedia.org/wiki/Vacuum_tube
6
Solid state transistor (triode)
• John Bardeen, William Shockley, and
Walter Brattain – Bell Labs – 1947
• Germanium (not Si) substrate
• Single crystal of Ge – with gold
electrical contacts
• Show voltage amplification
• Won Nobel prize in 1956 – 9 years later
• Further miniaturization – integration
http://en.wikipedia.org/wiki/History_of_the_transistor
7
Integrated circuits (ICs)
• IC – integrate different devices on a
single wafer – reduce size
• Devices – resistors, capacitors, diodes,
transistors – fabricated on single wafer
• Jack Kilby – Texas Instruments – Ge
IC – 5 components
• External wires – connections
First Si IC – Robert Noyce
• Si easily forms oxide – planar profile
• Use evaporated Al as wires – true
integration
http://en.wikipedia.org/wiki/Jack_Kilby
8
Kilby circuit
Robert Noyce IC
• Robert Noyce IC – teardrop design –
Horni transistor – evaporated metal
• Early 1960s – Si technology established –
stable devices
• Robert Noyce, Gorden Moore, and
Andrew Grove – founded Intel in 1968
• From 1960s – now – device
miniaturization
Microchip fabrication by Peter van Zant. McGraw-Hill professional, 5th edition, 2004
9
Moore’s law
Transistor density doubles
~ 2 years
http://en.wikipedia.org/wiki/Moore's law
http://en.wikipedia.org/wiki/Semiconductor_device_fabrication
10
Summary of some Intel ICs
45 nm → 32 nm → 22 nm → 14 nm → 11 nm
(under development)
11
Challenges in IC fabrication
• Wafer sizes increase – reduce
cost/chip
• Current – 300 mm or 12” wafers
• Future – 450 mm or 18” wafers
• Wafer handling and uniformity
12
• Metal interconnects ~ 11 layers
• Complexity in fabrication
Microchip fabrication by Peter van Zant. McGraw-Hill professional, 5th edition, 2004
http://electroiq.com/chipworks_real_chips_blog/2012/12/11/intel-details-22nm-trigate-socprocess-at-iedm/
Trigate transistors
• Smaller size – space is not enough in 2D
• Trigate transistors – 3D transistors
• Look at 3D integration – planar circuits joined in 3rd dimension
www.anandtech.com/show/4313/intel-announces-first-22nm-3d-trigate-transistorsshipping-in-2h-2011
13
Outline
• History of computers
• The age of Si
• Opto electronic devices
• Future technology
http://www.jantoo.com/cartoons/keywords/silicon-chip
14
Metals, semiconductors, and insulators
Material
Copper
Resistivity (ρ) (Ωm) • Classify materials based on electrical
properties
15.7 x 10-9
Silver
Gold
Silicon
14.6 x 10-9
22.8 x 10-9
0.1 - 103
Zinc oxide
Gallium
Arsenide
Wood
(damp)
Glass
10-2 – 10-4
10-6 – 10-2
15
103 – 104
1010 - 1014
• Resistivity (ρ) – dimension independent
• Metals – low ρ
• Semiconductors
• Insulators
• Temperature dependence
• Metals – ρ ↑ as T ↑
• Semiconductors – ρ ↓ as T ↑
• Semiconductors and insulators –
difference is arbitrary
Band picture of materials
Semiconductors/
Insulators
Metals
• Metals have continuous states – electrons can move easily. Halffilled bands. Good conductors
• Semiconductors – band gap between full and empty states.
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition, 2006
16
Direct vs. indirect semiconductors
CB
VB
CB
VB
• In Si – VB and CB edges do not coincide – indirect band gap
• In GaAs – VB and CB edges coincide – direct band gap – good for
optical applications
Fundamentals of semiconductors by Yu and Cardona. Springer, 4th edition, 2010
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So why Si?
• Si – band gap = 1.1 eV
• Indirect band gap – bad for optical
devices
• Abundant – as sand – 2nd most
abundant element – after oxygen
• Pure Si – poor conductor
• Add ‘impurities’ – drastic increase
in conductivity – stable i.e.
temperature independent
Si hybrid – sp3 orbitals –
valence and conduction band
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
18
p and n-type Si
e- move in VB (called holes)
e- move in CB
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition, 2006
http://www.redarc.com.au/solar/about/solarpanels/
19
Doping in Si
• Add ‘small’ amount of group V
(n-type) – 1 extra e-/atom
• Add ‘small’ amount of group III
(p-type) – 1 extra h+/atom
• Pure Si σ = 3 x 10-4 Ω-1m-1
• Add 20 ppb (parts per billion) of
As. New σ = 20 Ω-1m-1 – n-type
• 20 ppb – 1 As atom for every
5,00,00,000 Si atoms
• Same logic for p-type
http://chemistry.about.com/od/periodictable/ss/How-To-Use-A-Periodic-Table.htm
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Making Si
• Two challenges
• Need single crystal ultra pure Si
• Add ppb or ppm amount of dopants
• Starting materials – sand – SiO2
• Reduced with coke (C) – Si (impure)
• Purification – fluidized bed reactor – Si
(pure) but poly crystal
• Single crystal – Czochralski process –
single crystal ingot – also dope (n or p)
Microchip fabrication by Peter van Zant. McGraw-Hill professional, 5th edition, 2004
www.chipsetc.com/silicon-wafers.html
21
Diode – pn junction
Vacuum tube diode
rectifier
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
22
pn junction diode
• Diode – conducts current in one
direction
• When p side is connected to +ve
and n to –ve conducts – forward
bias
• When p side is connected to –ve
and n to +ve no conduction –
reverse bias
• Since both have Si – can make pn
junctions on same wafer – size
reduction
Semiconductor device physics and design by Mishra and Singh. Springer, 2008
23
Triode – transistor
Field
effect
transistor
(FET)
Vacuum tube triode
amplifier
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
24
Junction field effect transistor (JFET)
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
25
Metal oxide field effect transistor (MOSFET)
• JFETs – channel exists
• MOSFETs – channel
created by external bias
Metal oxide semiconductor
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
26
Conduction in MOSFET
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
27
IC microarchitecture
How diodes and triodes relate to computers?
• Computers work on Boolean logic
• Two states – 1 and 0, ON and OFF, T/F
(switch)
• Operators
• Arithmetic → +, –, x, % …..
• Logical → AND, OR, NOT, NAND……
• Can be built using diodes/triodes
• Input – Boolean representation
http://johndquan.com/blog/page/4/
28
AND gate
Truth table
Input 1 Input 2 Output
1
1
1
1
0
0
0
1
0
0
0
0
• 1 – ON – short circuit – high I/V
• 0 – OFF – open circuit – low I/V
Output will be ON (1) when only
A and B are ON (1)
http://en.wikipedia.org/wiki/AND_gate
29
OR gate
Truth table
Input 1 Input 2 Output
1
1
1
1
0
0
0
1
0
1
1
0
• 1 – ON – short circuit – high I/V
• 0 – OFF – open circuit – low I/V
Output will be ON (1) when
either A and B are ON (1)
http://en.wikipedia.org/wiki/AND_gate
30
Arithmetic operations
• Consider addition of two numbers – 3 and 5
• Convert 3 and 5 into binary equivalents
• 3 – 010
• 5 – 101
• Similar rules for other operations
• Use logic gates to implement this (made of
diodes/transistors)
Addition rules
0+0=0
0+1=1
1+0 = 1
1+1 = 0 (with carry over 1)
3
5
8
0
1
0
1
0
1
1
1
1
• Need storage elements
http://academic.evergreen.edu/projects/biophysics/technotes/misc/bin_math.htm
31
Memory elements – floating gate MOSFETs
•
•
•
•
•
Create a flash memory – read and re-write
Create MOSFET with 2 gates – control and floating
Writing –current stores charge (e–) in the gate – capacitor
Reading – measure capacitance to read the charge
Erasing – large reverse bias to remove the stored e–
http://en.wikipedia.org/wiki/Floating-gate_MOSFET
http://product.tdk.com/en/techjournal/archives/vol01_ssd/contents03.html
32
Si microarchitecture
• Diodes/transistors/resistors/
capacitors
• Build logic gates
• For operations
• Memory elements
• This forms Si
microarchitecture
•
• Die/Chip – different units –
functionality
•
• Each generation – reduce
size of components
Pentium IV die
http://www.chip-architect.com/news/2003_04_20_Looking_at_Intels_Prescott_part2.html
33
Outline
• History of computers
• The age of Si
• Opto electronic devices
• Future technology
http://www.cartoonstock.com/directory/l/let_there_be_light.asp
34
Optoelectronic devices
CB
VB
Absorb light
Emit light
LEDs, LASERs, Solar cells,
photo detectors
GaAs band diagram
35
Fundamentals of semiconductors by Yu and Cardona. Springer, 4th edition, 2010
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition,
2006
Samsung LED TV
World’s largest
110” 4K
UHD TV
• Resolution
3840x2160
•Refresh rate
120 Hz
•Dimensions
101.4" x 56'' x 3.5'‘
•LED backlight
http://www.amazon.com/Samsung-UN110S9-Framed-110-InchUltra/dp/B00L403O3A
36
LEDs – Light Emitting Diodes
RGB LED
37
LED light bulbs
http://en.wikipedia.org/wiki/Light-emitting_diode
http://myled.blog.com/2014/01/13/tips-to-buy-right-kind-of-led-strip-light/
http://en.wikipedia.org/wiki/LED_lamp. http://en.wikipedia.org/wiki/LED_Incapacitator
LEDs – pn junctions
• Basic structure is pn junction
• Carrier injection and
recombination – light
• Color – material dependent
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition, 2006
Physics of semiconductors by S.M. Sze and K.K. Ng, Wiley 3rd edition, 2007
38
2014 Nobel prize in Physics
The Nobel Prize in Physics 2014 –
“for the invention of efficient blue
light-emitting diodes which has
enabled bright and energy-saving
white light sources".
Doped GaN based blue LED
Grown by Hydride Vapor Phase
Epitaxy (HVPE) technique
Development of white light LEDs
http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/
39
Organic LEDs
OLED/
AMOLED
TVs
• Emissive & conductive
layers – organic
• Light weight
• Wider viewing angle
• No backlighting
• Lifetime is shorter
http://en.wikipedia.org/wiki/OLED
1 F. So et al. MRS Bulletin 33, 663 (2008)
40
OLED
lights1
Organic
molecules
LASERs – solid state
Laser pointers1
IR lasers – fiber optics –
communication2
1http://commons.wikimedia.org/wiki/Laser_pointer
2
41
http://en.wikipedia.org/wiki/Optical_fiber
Laser arrays –
welding1
LASERs – working principle
Light Amplification by
Stimulated emission of Radiation
Wavelength decided by band gap
Physics of semiconductors by S.M. Sze and K.K. Ng, Wiley 3rd edition, 2007
42
LASER – device structure
Fabrey Perot optical cavity
Total internal reflection
Quantum well1, wire, and dot lasers
Physics of semiconductors by S.M. Sze and K.K. Ng, Wiley 3rd edition, 2007
1Nature Photonics 3, 432 (2009).
43
Solar cells
http://en.wikipedia.org/wiki/Solar_cell. http://en.wikipedia.org/wiki/Sunlight
http://phys.org/news/2011-10-france-vast-solar-panel-array.html
44
Solar cell efficiencies
http://en.wikipedia.org/wiki/Solar_cell
45
Solar cells - principles
•
•
•
•
Reverse of LED and LASER
Light – converted to carriers
Different designs & materials
Cost vs. efficiency
Principles of electronic materials by S.O. Kasap. McGraw-Hill professional, 3rd edition, 2006
http://home.howstuffworks.com/solar-light2.htm
46
Outline
• History of computers
• The age of Si
• Opto electronic devices
• Future technology
http://lazytechguys.com/news/the-future-of-technology-cartoon
47
Top down fabrication
48
Bottom up fabrication
Self assembly of molecules 1
Self assembly of atoms 2
Different substrates can be used
1
E.V. Shevchenko et al. Nature 439, 55 (2006)
2 http://researcher.watson.ibm.com/researcher/view_group_subpage.php?id=4252
49
Stretchable semiconductors
Si1
NIR
emitter
1
W.M. Choi et al. Nano Lett 7, 1655 (2007)
J. Yoon et al. Nature 465, 329 (2010)
50
http://rogers.matse.illinois.edu/
Bendable semiconductors
“Electronic
eye” – Si
pn junction2
GaAs solar cell on PET1
Stretchable Si – twisting does not damage the
circuit3
1J.
51
Yoon et al. Nature 465, 329 (2010)
2 H.C. Ko et al. Nature 454, 748 (2008)
3 D.H. Kim et al. Nature 320, 507 (2008)
http://rogers.matse.illinois.edu/
Flexible electronics – applications
Battery used to power a pace
maker – delay replacement
Flexible piezoelectric battery
1C.
52
Dagdeviran et al. PNAS 111, 1927 (2014)
Micro lighting – extreme conditions
1R.H.
53
Kim et al. Nature mater. 9, 929 (2010)
Printed electronics
• Bottom up fabrication approach
• Inkjet printer
• Thermal printing
• Piezoelectric printing
• Inks
• Metals
• Semiconductors
• Insulators
• Polymers
• Organics
• Low material wastage, simple
http://spie.org/x18497.xml
B.Y. Ahn et al. Science 323, 1590 (2009)
54
Printed metals
RT
650 °C
Printed silver lines1
1B.Y. Ahn
55
et al. Science 323, 1590 (2009)
Printed silver lines
• Commercial silver
ink from Methode
Development
Company
• Modified Epson
printer
• Printing on different
substrates
Silver on photo paper
A. Sundar, S. Sharma, and P. Swaminathan unpublished
56
• Drying at room
temperature ~ 10
minutes
Printed memory devices
D.H. Lien et al. ACS Nano 8, 7613 (2014)
57
Printed organic LEDs (OLEDs)
1Spin
casting
organic layer
Cadmium
selenide
Qdots –
color
depends on
size
2Printed
organic solar
cell
1X.
Yang et al. ACS Nano 8, 8224 (2014)
2L. Leonat et al. J. Phys Chem C 118, 16813 (2014)
58
Future shock – wearable technology
Apple watch –
release date 20151
Samsung watch –
available2
Apple bracelet –
release date (?)
Stick on circuit – band
aid3
1https://www.apple.com/in/watch/
2https://www.samsungindiaestore.com/
59
3http://www.ecouterre.com/bandaid-like-stick-on-circuit-board-turns-your-body-into-a-gadget/
Future shock – paper electronics
Backlight LEDs
Microfluidics
Paper battery1
Paper solar cells
http://spectrum.ieee.org/semiconductors/materials/electronics-on-paper
1http://www.powerpaper.cn/
60
Summary
• History of computers
• The age of Si
• Opto electronic devices
• Future technology
http://www.glasbergen.com/education-cartoons/education-technology/
http://www.glasbergen.com/education-cartoons/
61
NPTEL course
Online course on Electronic materials, devices, and fabrication
http://nptel.ac.in/courses/113106062/
62
NPTEL Course on YouTube
Course also available on YouTube
search = “NPTEL + Parasuraman”
http://www.youtube.com/playlist?list=PLbMVogVj5nJTqQc4Takon3QAhrtOLBV4M
63
PDF notes
Course notes in PDF form are available in my website (incomplete)
URL: http://mme.iitm.ac.in/swamnthn/
http://mme.iitm.ac.in/swamnthn/
64

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