Advanced LED structures materials fabrication lighting and other

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 Structures §Surface emitting §Edge emitting § superluminescent diode §Packages ◦ Traditional ◦ Surface Mount

Materials Aluminum gallium arsenide Aluminum gallium indium phosphide Aluminum gallium nitride Aluminum nitride 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(Al. N, In. N, Ga. N): 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 Applications §Optical 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 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

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Key Points 1. 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