Introduction to Optoelectronic Devices

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Introduction to Optoelectronic Devices

• Jing Bai
• ECE Assistant Professor
• Office MWAH 255
• Tel [phone]
• Email jingbai_at_d.umn.edu

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What Did the Word Opto-Electronics Mean?

• Optoelectronics is the study and application of
  electronic devices that interact with light

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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 a semiconductor
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
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 semiconductor
material
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Operation Principle of LED
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Semiconductor Materials vs. LED Color
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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)
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Laser Cavity Design
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Photo Diodes (PDs)
A photodiode is a semiconductor diode that
functions as a photodetector. 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
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Solar Energy Spectrum
Solar radiation outside the earths surface 1.35
kW/m2, 6500 times larger than worlds energy
demand
Spectrum of the solar energy
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)
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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 (QCLs) a New Light
Generation Mechanism
Cascading effect

• Advantages
• Wavelength depends on layer thickness (flexible
  design)
• Well-mastered materials can be used for long
  wavelength
• Multiple colors can be generated in same laser
• High output power due to cascading effect

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Applications of QCL
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Quantum Dot Superlattice Solar Cell
Au grid bar
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Quantum Dot Superlattice Solar Cell
ECV
Band structure of quantum dot superlattices
Current-voltage relationship