How is led made

An electron hole exists where an atom lacks electrons negatively charged and therefore has a positive charge. Semiconductor materials like germanium or silicon can be "doped" to create and control the number of electron holes. Doping is the adding of other elements to the semiconductor material to change its properties.

By doping a semiconductor you can make two separate types of semiconductors in the same crystal. The boundary between the two types is called a p-n junction. The junction only allows current to pass through it one way, this is why they are used as diodes.

LEDs are made using p-n junctions. As electrons pass through one crystal to the other they fill electron holes. They emit photons light.

This is also how the semiconductor laser works. Above: A laser also creates light, but through a different construction. Read more about semiconductor devices used in electronics here.

To understand p-n junctions and semiconductors better you will need to invest a good amount of time in a lecture, it is not a simple phenomena and far too lengthy to cover here.

See a 59 minute introduction lecture to solid state semiconductors here. Phosphors are used to help filter the light output of the LED. They create a more pure "harsh" color. Engineers had to figure out how to control the angle the light escapes the semiconductor, this "light cone" is very narrow. They figured out how to make light refract or bounce off all surfaces of the semiconductor crystal to intensify the light output. This is why LED displays traditionally have been best viewed from one angle.

The metal tabs on the sides of each help distribute the heat away from the LED. Photo: Whelan Communications. This type of display is only usable for large area applications and decorative backgrounds in small spaces. The human eye can only effectively perceive the image at more than 6 meters distance.

The tricolor array is arranged in the close-up at the top right. There are also orange, green, blue, violet, purple, ultraviolet LEDs. For more details on elements used for each color go here. Above: Two different types of LEDs, both in a strip mount configuration. Above: this experiment of a tunnel diode atop a GaAs semi-insulating substrate convinced Pittman and Biard that there must be light emission going on, and resulted in further experimentation.

The early years of the s consisted of a 'race' in the field of semiconductors. Gallium arsenide and germanium were some of the first semiconductors uses before silicon became the preferred material in the industry. These devices were being developed as diodes since they can pass current in one direction by not the other. Biard and Gary Pittman. Gary had been working in the related field of solar cells since In their efforts to try to make an X-band GaAs varactor diode they created tunnel diodes which had been developed first at Esaki.

They placed the tunnel diode on a GaAs substrate and discovered that there must be light production going on during forward bias operation. Using an infrared detector just brought in from Japan they tested it and discovered that the devices lit up brightly!

The LEDs were first used with IBM computers to replace tungsten bulbs that controlled punch card readers infrared light was sent through the holes, or blocked by the card. Today there is a myriad of applications for the LED. The First LED patent click to enlarge. Above: Walter T. Matzen top and Bob Biard bottom worked on parametric amplifiers, this helped lay groundwork for the LED. Later Gary Pittman and Mr.

Biard worked on varactor diodes which led to the LED as we know it. Read the full story of their work with this PDF here. Round discovered electroluminescence when using silicon carbide and a cats whisker. Oleg Losev independently discovered the phenomena the same year. London, United Kingdom. Losev studied the phenomena of light emitting diodes in radio sets. In he published a detailed report but his work was not well known until the s when his papers resurfaced. Saint Petersburg, Russia.

This was the first modern LED. The discovery was made during a test of a tunnel diode using a zinc diffused area of a GaAs Gallium Arsenide semi-insulating substrate. Dallas, Texas. Photo: Robert Biard. He had started working in with semiconductor GaAs for the creation of early solar cells. General Electric. Syracuse, New York. The types and varieties of LEDs grow every day it seems, but today we are taking it back to the basics. LED lighting and incandescent and fluorescent lights are not only designed differently, they create light differently.

Traditional lighting creates light by attaching wires to a source of energy. When the wires heat up, they emit light. LEDs create light by electronic excitation as opposed to heat. This is why LEDs use less energy and emit less heat, as heat is not a main component in creating light. LED stands for light emitting diode. Therefore, LED lights are made up of small diodes. Each diode is created from semiconductor material.

One of the layers of semiconductor material will have an excess of electrons, one layer will be depleted of electrons. This difference in electron levels allows electrons to move from one layer to the next, creating light through electronic excitation mentioned above. To break it down a little further, the semiconductor material itself is made of crystalline material and needs impurities in order to conduct electricity.

However, these impurities are added to the semiconductor material later on in the manufacturing process. However, do not mistake these impurities as imperfections in the semiconductor material. They do not lessen the value of the diode, they enhance it! Adding these impurities to the semiconductor is called doping and it is an essential material used in the making of LEDs.

The most common impurities added are zinc and nitrogen. Finally, in order to power the diodes, electrical wires must be added. Gold and silver compounds are often used in LED wires, as they can handle being soldered and heat well. Lastly, to finish it off, the diodes are encased in a transparent plastic, not glass like traditional bulbs, making them durable and long-lasting.

When designing LED lights, there is a bit more creativity allowed. Depending on the application of the light, color temperature, brightness and efficiency are decided before any manufacturing takes place. These attributes are decided based on the size of the diode, the semiconductor material used, the types of impurities added and and the thickness of diode layers.

First and foremost, the semiconductor material must be made. This is called the semiconductor wafer. Cole, Bernard C. October, , p. Iversen, Wesley R. September 18, Marston, Ray. January, , p. Weisburd, Stefi. May 9, , p. Toggle navigation. One way to add the necessary impurities to the semiconductor crystal is to grow additional layers of crystal onto the wafer surface.

Although the average lifetime of a small light bulb is years, a modern LED should last years or more before it fails. Periodicals Cole, Bernard C. Other articles you might like:. User Contributions: 1. Faiz Ahmed. The article is outstanding. Before reading this article, I had no idea about LED. As we are short of Electricity, I thought the country can be immensely benefit from low electric consumption using LED bulbs and lights for houses and offices.

We want to set up a manufacturing plant in Bangladesh if you can guide us to procure required equipments. Lester Choc. Hey nice Article!

It would be nice to have more pictures. It is a really nice I hope to see something like this on the show How it's made though I would assume it would be hard to get shots in high pressurized chambers for the LED.

Anyways check out DrChoc. Of all the materials used to make LED lights, which are the most costly to use and which are used by the highest volume or quantity? Very nicely explained. Details are to the miniscule. Can any one tell me where can I get a complete turnkey project for manufacturing. Pramod G. Nice Article! I need to know different kinds of machines to manufacture LED bulb? Where can one get the machines and is there training available when you purchase one?

If you have a list please send and the prices. Claudio Righetti. There are claims that all LEDs only produce UV light, and that the thin coating of phosphor found inside the covering lens, or dome is what priduces the usablw light that we see.

If this is correct, could the deterioration or cracking of the layer of phosphor inside the lens cause UV light to escape? And if so, could the UV light cause eye damage? Your comments are welcome. Nice details about manufecturing of LED lights. Vimal Kumar. I'm interested in LEDs manufacture! But I didn't getting the proper details how to manufacture ando about easy machines! Your forums and details are appreciable but need an easy machinaries.

Madehow, really appreciate you putting all these detail together in structured way and in simple language. Possibly also share the details about the companies who can help with machinery and other row material required. Comment about this article, ask questions, or add new information about this topic: Name:. E-mail: Show my email publicly. Human Verification:. Public Comment: characters.