15 May 2008

Did you say white LED?

The LEDs (Light Emitting Diode) are semi-conductor diodes that emit light when traversed by a current flow. A photo emission is taking place at the diode PN junction region, and the total quantity of emitted photons, therefore the light intensity, is proportional to the current intensity that passes through it.

The spectrum of the emitted light is primarily defined by the type of materials used to build the diode's PN junction, although it also depends on the current’s intensity and on the junction temperature.

LED manufacturing uses diverse technological process variations that lead to the production of different families of light color, such as:

  • Gallium arsenide (GaAs) for light from infrared to red (650 nm);
  • Gallium arsenide and phosphate (GaAsP) for light from red to yellow (630-590 nm);
  • Gallium phosphate (GaP) for wavelength from blue to green (565 nm);
  • Gallium nitride (GaN) for blue light (430nm);
  • Indium and Gallium nitride (InGaN) for light from deep blue to ultraviolet (390 – 360nm);

The white power LEDs are usually based on blue LED chips of the more recently introduced InGaN family. The white color is produced using a blue light chip covered by one or more semi-transparent layers of phosphors. Using the light’s complementary color combination, appropriately chosen phosphors layers combined with the base blue light allow the creation of various white lights.

As a result, today’s white power LEDs generally behave like the InGaN products' family, with some variations, due to the presence of the phosphors.

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Form is the visual shape of mass and volume. Light makes form legible. There is no form without light.


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