LED WAFER
Last updated 12-09-12


The photographs below show the LED "wafer" - what you see before getting to the finished LEDs.

In general, the LED structure is the compound semiconductor epitaxial film grown on suitable substrate. Two most modern techniques that have become the workhorses for production of the most advanced devices (including LEDs) are molecular beam epitaxy (MBE) and metal organic chemical vapour deposition (MOCVD).

The visible LED has come a long way since its introduction just over 40 years ago and has yet to show any signs of slowing down. A Blue LED, which has only recently become available in production quantities, will result in an entire generation of new applications. Blue LEDs because of their high photon energies (>2.5eV) and relatively low eye sensitivity have always been difficult to manufacture. In addition the technology necessary to fabricate these LEDs is very different and far less advanced than standard LED materials. The blue LEDs available today consist of GaN (gallium nitride) construction with brightness levels in excess of 5000mcd at 20mA for GaN devices. Since blue is one of the primary colors, (the other two being red and green), full color solid state LED signs, TV’s, very large displays etc. became commercially available. Other applications for blue LEDs include medical diagnostic equipment and photolithography. It is also possible to produce other colors using the same basic GaN technology and growth processes. For example, a high brightness blue-green (approximately 500nm) LED has been developed that is currently being evaluated for use as a replacement to the green bulb in traffic lights. Other colors including purple and white are also possible. It is possible to create every color with LEDs by combining red, green and blue (RGB), which can create white light and all other colors. RGB technology is an improvement over the old technology of creating white light by combining blue with a coating that fluoresces (glows) yellow. - the way white LEDs currently work.

UV (ultraviolet) LEDs have a very similar construction to blue LEDs, but there is even less of the metal called indium in their construction.

The wafer shown in these photographs was developed using a Hydride Vapour Phase Epitaxy process (HVPE) as opposed to MOCVD (Metal Oxide Chemical Vapour Deposition) or MBE (Molecular Beam Epitaxy). The following site contains a brief synopsis of the HVPE process and the difference between it and MOCVD:
www.thefoxgroupinc.com/t1.html (link opens in a new window).

Another main advantage of the HVPE manufacturing process is the consistency of the LED wafers made by HVPE. The peak wavelength has a tolerance of no more than +/- 2nm and the Forward Voltage has a tolerance of +/- 0.2V. This eliminates binning requirements for most applications and greatly facilitates design work while reducing costs.

Just for {vulgar term for multiple feces} and giggles, I irradiated the wafer with 409nm NUV (near-ultraviolet) radiation from my Blu-ray Portable Laser to check for fluorescence, and none was detected.



This is an example of an LED wafer. It consists of ~20,000 LEDs, not yet cut from the wafer.
Sample graciously donated by B. O'Meara of The Fox Group.



Same as above, but magnified, so you can see the LED mesas on the wafer.
Sample graciously donated by B. O'Meara of The Fox Group.



Here's another close-up of the wafer's surface, showing some of the LED mesas.
Sample graciously donated by B. O'Meara of The Fox Group.



Here's another photograph of the wafer.




Here's another close-up of the wafer's surface, showing some of the LED mesas (6x macro plus a positive {magnifying} lens held in front of the camera's own lens.




Here's yet another close-up of the wafer's surface, showing some of the LED mesas (6x macro plus a positive {magnifying} lens held in front of the camera's own lens.








Do you manufacture or sell an LED flashlight, task light, utility light, or module of some kind? Want to see it tested by a real person, under real working conditions? Do you then want to see how your light did? If you have a sample available for this type of real-world, real-time testing, please contact me at ledmuseum@gmail.com.

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WHITE 5500-6500K InGaN+phosphor 
ULTRAVIOLET 370-390nm GaN 
BLUE 430nm GaN+SiC
BLUE 450 and 473nm InGaN
BLUE Silicon Carbide
TURQUOISE 495-505nm InGaN
GREEN 525nm InGaN 
YELLOW-GREEN 555-575mn GaAsP & related
YELLOW 585-595nm
AMBER 595-605nm
ORANGE 605-620nm
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RED 640-700nm
INFRARED 700-1300nm
True RGB Full Color LED
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Where to buy these LEDs 
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