Advanced LED structures, materials, fabrication, lighting and other applications

BY: GARETT HENRIKSEN

5/4/2015

Abstract Light Emitting diodes are a semiconductor light source that emit light when the PN-junction is

activated. This presentation will explain how LEDs are made, the materials that they are made

out of, the structure that makes them what they are, and how the light that they create is used.

Outline

Structures

Materials

Fabrication

Lighting

Other Applications

Advantages and Disadvantages

LED StructuresSurface emitting

Edge emitting superluminescent diode

Packages◦ Traditional◦ Surface Mount

MaterialsAluminum gallium arsenide

Aluminum gallium indium phosphide

Aluminum gallium nitride

Aluminum nitride

Gallium arsenide

Gallium arsenide phosphide

Gallium phosphide

Indium gallium nitride

Indium gallium phosphide

LEDs can be made up from group III and V elements from the periodic table.

III-Nitride semiconductors(AlN, InN, GaN): Can create LEDs to cover the ultraviolet to the entire visible spectrum.

Fabrication Grown on sapphire, silicon carbide

Process to create layers:◦ Molecular beam epitaxy◦ Metal organic chemical vapor deposition◦ Liquid phase epitaxy

Lighting Aviation lighting

Automotive headlights

Traffic signals

Camera flashes

Other ApplicationsOptical fiber applications

Medical diagnostic equipment

Photolithography

Detecting light

Displays◦ 7 segment ◦ Star-burst◦ Dot matrix◦ TV’s

Advantages and Disadvantages Advantages:

More light per watt

Faster switching

LEDs emit light in a certain direction

Internal reflectors

Disadvantages:

Cost

Harder to design

Summary◦ The two types of LEDs are surface and edge emitting. They can packaged traditionally or surfaced

mounted.◦ When a current is applied to the PN-junction then the holes and electrons combine making photons.◦ Many LEDs can be combined to make a display.◦ The materials used come from the III and V groups on the periodic table◦ Crystal layers are formed using liquid phase epitaxy◦ The final epoxy protects the tiny electronics and keeps everything together◦ LEDs for lighting are much more efficient than incandescent or florescent

References http://electroiq.com/blog/2010/07/production-metrology/

http://phostec.eu/downloadcenter/tsf_led.pdf

http://energy.gov/sites/prod/files/2015/02/f19/haugaard_led-materials_sanfrancisco2015.pdf

https://www.energystar.gov/index.cfm?c=lighting.pr_what_are

http://spectrum.ieee.org/semiconductors/optoelectronics/the-leds-dark-secret

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5699639

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6551030

http://www.soraa.com/public/docs/History-of-GaN-LEDs-IEEE-2013.pdf

http://www.radio-electronics.com/info/data/semicond/leds-light-emitting-diodes/structure-fabrication.php

http://www.rp-photonics.com/light_emitting_diodes.html

http://iopscience.iop.org/2043-6262/1/2/025015/pdf/2043-6262_1_2_025015.pdf

http://www.madehow.com/Volume-1/Light-Emitting-Diode-LED.html

http://www.cnet.com/news/appliance-science-how-led-lights-work/

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/leds.html

http://www.ele.uri.edu/~vijay/ELE432_Report_LED.pdf

http://www.tpub.com/neets/tm/110-4.htm

http://iopscience.iop.org/2043-6262/1/2/025015/pdf/2043-6262_1_2_025015.pdf

Key Points1. The two types of LED structures are surface emitting and edge emitting.

2. Electrons and holes combine, the electron loses energy to create a photon.

3. Direct band gaps create the most amount of photons

4. LED’s are taking over house lighting because they are so much more efficient

5. The color of light emitted from an led is determined by the band gap of the semiconductor