Introduction to Op to Electronics

8/8/2019 Introduction to Op to Electronics

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Introduction toOptoelectronic Devices

Jing Bai

ECE Assistant Professor

Office: MWAH 255Tel: (218)726-8606

Email: [email protected]


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Outline

What is the optoelectronics?

Major optoelectronic devices

Current trend on optoelectronic

devices

My current research work on

nanoscale optoelectronic devices


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What Did the Word Opto-

Electronics Mean?

Optoelectronics is the study and application of

electronic devices that interact with light

Electronics

(electrons)

Optics

(light or photons)

Optoelectronics


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Examples of Optoelectronic Devices


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Major Optoelectronic Devices

Direct Conversion Between Electrons and Photons

Light-emitting diodes (LEDs)

(display, lighting,)

Laser diodes (LDs)

(data storage, telecommunication, )

Photodiodes (PDs)

(telecommunication, )

Solar Cells

(energy conversion)


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Light-Emitting Diodes (LEDs)

Light-emitting diode (LED)is asemiconductor diode that emits

incoherent narrow-spectrum light

when electrically biased in the

forward direction of the p-n junction.


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Photon Emission in Semiconductor

EF

EC

EV

Conduction

band

Valenceband

Photon

Eg

When an electron meets a

hole, it falls into a lower

energy level, and releases

energy in the form of a

photon.

The wavelength of the light

depends on the band gap

of the semiconductormaterial

Semiconductor materials: Si, Ge, GaAs, InGaAs, AlGaAs, InP, SiGe, etc


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Operation Principle of LED


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Semiconductor Materials vs.

LED ColorGeneral Brightness

GaP GaN GaAs GaAIAs --

Green, Red Blue Red, Infrared Red, Infrared --

Super Brightness

GaAIAs GaAsP GaN InGaN GaP

Red Red,Yellow Blue Green Green

Ultra Brightness

GaAIAs InGaAIP GaN InGaN --

Red Red,Yellow, Orange Blue Green --


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Application of LEDs

Display

Solid-state lighting

Communication

Remote control, etc

LED lights on an Audi S6


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Laser Diodes (LDs)

Lasers (Light Amplification by Stimulated Emission)

Photon emission processes:

Absorption

Photodetectors

Spontaneous emission

LEDsStimulated emission

Lasers


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Laser Cavity Design


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Photo Diodes (PDs)

A photodiode is a semiconductor diode that functions as aphotodetector. It is a p-n junction or p-i-n structure. When a

photon of sufficient energy strikes the diode, it excites an

electron thereby creating a mobile electron and a positively

charged electron hole


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Operation Principle of a PD


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PDs Detection Range and Materials

Material Wavelength range (nm)

Silicon (Si) 1901100

Germanium (Ge) 4001700

Indium gallium arsenide(InGaAs)

Lead sulfide (PbS)

8002600


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Solar Energy Spectrum

Spectrum of the solar energy

Solar radiation outside

the earths surface:

1.35 kW/m2, 6500 times

larger than worldsenergy demand

AM0: radiation above the earths atmosphere

AM1.5: radiation at the earths surface

Blackbody radiation: ideal radiation


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Vision of Solar Cells (Photovoltaics)

Solar Energy Free

Essentially Unlimited

Not Localized

Solar Cells

Direct Conversion of Sunlight Electricity No Pollution

No Release of Greenhouse-effect Gases

No Waste or Heat Disposal Problems

No Noise Pollution very few or nomoving parts

No transmission losses on-SiteInstallation

Why solar cells?


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Operation Principle of Solar Cells


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Residential and Commercial Applications

Challenges:

cost reduction via: a) economy of scales b) building integration and

c) high efficiency cells


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Trends in optoelectronic devices

Long wavelength, high power light sources or

photodetectors

Nanoscale devices Low cost, easy fabricated materials

High opto-electronic conversion efficiency

Multi-wavelength sources

Next, my current research topic

nanoscale optoelectronic devices


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Quantum Cascade Lasers MIR Light Emission

50.0

UV (FIR)VIS NIR

40.0

30.0

20.0

10.03

.0

2.0

1.5

0.7

0.3

0.4

0.5

0.6

WaveLe

ng

th(

m)

MIR (3~30 m)

Part of the SpectrumSun

The wavelength of quantum cascades laser lies in

the mid-Infrared (MIR) region (3~30 m)

Many chemical gases have strong absorption in

mid-infrared region, such as CO,NH3,

, NO, SO2,

, etc.


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Quantum Cascade Lasers (QCLs)

a New Light Generation Mechanism

Quantum well laser

Interband transition

QCL Intersubband

transitionCascading effect

Advantages:

Wavelength depends on layer thickness (flexible design)

Well-mastered materials can be used for long wavelength

Multiple colorscan begenerated in same laser

High output power due to cascading effect


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Applications of QCL

Environmental sensing and pollution monitoring

Industrial process control

Automotive

Combustion control, catalytic converter diagnostics

Collision avoidance radar, cruise control

Medical applications

Breath analysis; early detection of ulcers, colon cancer, etc.

Military and law enforcement

QCL for gas detection


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Quantum Dot Superlattice Solar Cell

Au grid bar

p+ GaAs substrate

100 nm p GaAs

100 nm n GaAs

30 nm n GaInP

200 nm n+ GaAs

Aucontact

Si: GaAs

Si: GaAs

Si: GaAsSi: GaAs0.5 m intrinsic

region containing

50 layers of

quantum dot layers


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Quantum Dot Superlattice Solar Cell

ECV

CB

VB

IB

ECI

EIVh(

1+

2)

orh3

Current-voltage relationship

Band structure of quantum

dot superlattices

Introduction to Op to Electronics

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