Transcript ENERGY MANAGEMENT POTENTIAL FOR PAKISTAN

New trends in Optoelectronics
DR SALEEM FAROOQ SHAUKAT
COMSATS
Optics + Electronics
Main important industry of 21st century
Far wider meaning and more applications
than just optical communications, storing,
displaying, printing images,
 information
retrieval,
processing,
transport, internet, CD, DVD, digital
camera and flat panel displays, etc.
 Human
characteristics, such as
fingerprint
identification,
facial
recognition, iris recognition, retina
scanning, e-banking, online shopping
 In
medicine, various types of lasers are being
used in corneal reshaping, dentistry,
dermatology, urology and cardiology
 According
to
Optoelectronics Industry
Development Association (OIDA), USA,
optoelectronics industry will bring $460
billion by 2010. This represents a compound
annual growth rate of 9.5%
 Data
storage, A remote sensing satellite
sends down more than 1 Gbyte of
images data per second
 Displaying
the image, pixels
Photonics

Photonics is the science and technology of
generating, controlling, and detecting photons,
particularly in the visible light and near infra-red
spectrum

Photons carry information at the speed of light and
two photons don’t interfere each other

An optical computer is a computer that uses
photons / light, instead of electricity, to perform
computations
Photonic Integrated Circuit
Applications of Photonics
 Consumer
Equipment: Barcode
scanner, printer, CD/DVD/Blu-ray
devices, remote control devices
 Telecommunications: Optical fiber
communications
 Medicine: correction of poor eyesight,
laser surgery, surgical endoscopy,
tattoo removal
Applications of Photonics
 Industrial
manufacturing: the use of
lasers for welding, drilling, cutting, and
various kinds of surface modification
 Construction: laser levelling, laser
rangefinding, smart structures
 Aviation: photonic gyroscopes lacking
any moving parts
 Military: IR sensors, command and
control, navigation, search and rescue,
mine laying and detection
Applications of Photonics
 Entertainment:
laser shows, beam
effects, holographic art
 Information processing
 Metrology: time and frequency
measurements, rangefinding
 Photonic computing: clock distribution
and communication between computers,
circuit boards, or within optoelectronic
integrated circuits; in the future:
quantum computing
Refraction of photons by a prism
Optical Communication
 Creating
the
optical
signal
using
a
transmitter
 Relaying
the signal along the fiber
 Receiving
the optical signal and converting
it into an electrical signal
 The
most commonly used optical transmitters are
semiconductor devices such as Light-emitting
diodes (LEDs) and laser diodes
 The
main component of an optical receiver is a
photodetector that converts light into electricity
through the photoelectric effect
 The
impact is more on the broadband
information services
 The
fourth generation of fiber-optic
communication systems used the
wavelength-division multiplexing to
increase fiber capacity
 Wavelength-division
multiplexing (WDM) is the
practice of dividing the wavelength capacity of an
optical fiber into multiple channels in order to
send more than one signal over the same fiber

Systems with more than 8 active wavelengths per
fiber are generally considered Dense WDM
(DWDM)
Wavelength Division Multiplexing
Another presentation of Wavelength
Division Multiplexing phenomenon
 Remarkable
progress has been made in the field of
optical communication system
 Today,
the capacity of optical communications has
expanded gigabits per second into terabits per
second, enough to meet the current traffic demand
due to the explosive growth of data transfer and
internet services
Wavelength Division Multiplexing
& Deplexing
Inexpensive
disposable fiber optics can
relay real time information about drilling
process
Optoelectronics
field provides a wealth of
opportunities for scientists, technologists
and those with modern manufacturing skills.
One can work across a number of different
disciplines
Emerging Disciplines
Recognition
of human characteristics
(finger print, face iris, hand geometry)
Surveillance
Lip
and tracking
reading and behavioral analysis
Tagging of targets and network
implications
Rapid analysis of video information
Pattern recognition
Broadband optical communication and
networks
Laser communication
Trends in holography
Optical
signal processing
Optical
instrumentation and metrology
DVDs
and blu-ray discs
Trends
in optical memory
Light Emitting Diodes (LEDs)
 Silicon
is the most abundant elemental
semiconductor and makes 21 % of earth crust
 Porous
Silicon (P S) is an interconnected
network of air holes in silicon. The size of
these air holes, called pores, is of a few
nanometers
P S
offer promises of powerful
NANOTECHNOLOGY tool

The production of long life, stable and highly
efficient electroluminescence (EL )
Fabrication of Porous Silicon
 Silicon
wafers used were 1 inch diameter
(111)- oriented n-type substrate with
resistivities between 5 – 10 Ωcm
 Porous
Silicon (PS) is formed during
electrochemical dissolution of silicon in
Hydrogen Fluoride (HF) based solution
 PS
formation results from the passivation of
insoluble silicates in the pore walls.
 PS
formation is due to reverse bias break
down in n-type silicon.
 Hydrogen
plays an important role in the
surface formation of PS
 The
back side of the Si wafer acts as a
secondary cathode and the front side as
secondary anode
 PS
formed layer was of 3 to 5 microns
observed by SEM
Fabrication of Porous Silicon:
ANODIZATION CELL
Schematic diagram of a double-tank cell
 A number
of direct contacting schemes have
been tried: semi transparent metal layers,
indium tin oxide, silicon carbide and
conducting polymers
 Poly-4-dicyanomethylene-4H-cyclopenta
dithiophene monolayer (PCDM) is a good
candidate for fabrication of a transparent
conducting contact to PS
 PCDM
has a transmission window over
part of the visible spectrum
 PS
and PCDM contact make a good p-n
junction
 SEM
shows that a PCDM coated surface is
smoother than bare porous silicon
EXPERIMENTAL
Schematic structure of Au/PCDM/Si/Al
 A layer
of Al evaporated on the back of the
substrate and annealed at 500 oC to make an
ohmic contact
 PCDM
dissolved in nitrobenzene was used for
wetting the PS layer
 A very
thin layer of Au was evaporated on the
PCDM to make a better contact
Electroluminescence from PS
 The
deposition of PCDM provides not only
electrons under the external electric field but
holes as well
 The
presence of PCDM results in a higher
electron hole recombination rate, a higher
intensity emission and a larger emission rate
 Red
/ orange stable luminescence bands
originating from the recombination in the Si
crystal nanostructure
 Emission
area significantly large.
In Sn PS
Intensity (a.u.)
1000
PCDM
800
600
400
200
0
400
500
600
700
800
900
1000
Wavelength (nm)
EL of PCDM coated porous Si (solid line) compared
with that of In Sn porous Si (dotted line)
Electrical Measurements

Electrical transport characteristics show Schottky
behavior.

The Schottky junction provides more chance for
carriers passing through the nanowire surface and
more electron-hole recombination occurs. This
increases both the brightness and emission area of
the Nano-wire based Photonic devices

The rectification ratio at ± 15 V is 450
Current (mA)
-15
700
600
500
400
300
200
100
0
-100
-5
5
15
25
35
Voltage (V)
I–V characteristics of typical Au/PCDM/PS/Si/Al LED,
showing rectifying behavior
Structural Studies
Cross-sectional micrographs (High Resolution Scanning Electron
Microscope) of PS layers obtained from Si Substrate
APPLICATIONS
Sensors
 Solar Cells
 Memory Chips
 Optical switches
 Photonic Devices
 Coupling Devices, coupling light and electronics
to build very fast optoelectronics devices

CONCLUSIONS

EL has been observed from Au-PCDM-PS-SiAl device structures

More stable than any reported solid PS-based
contact LED

Visible light emission can be observed under
normal daylight

Electrical transport characteristics show
Schottky behavior

The rectification ratio at ± 15 V is 450

The time stability and reproducibility was good
for all the devices tested

PCDM is a very promising material for
stabilizing PS devices
Thank You