Make the Chip
All LEDs start with a semiconductor substrate—essentially, a material that conducts electricity. On top of that substrate, which typically ranges in diameter from 100 millimeters to 400 millimeters, manufacturers trigger chemical reactions to grow an epitaxial layer. The crystal structure of this epitaxial layer will be responsible for the movement of electrons that ultimately creates light. Once this layer has formed, over a duration of time that is generally kept proprietary, manufacturers cut the semiconductor wafer into several individual LED chips.
Mount the LED Chip
On its own, the semiconductor wafer doesn’t do anything. It needs electricity to emit light. To make the LED chip usable as a light source, manufacturers mount it onto a base with a power source. Typically, the base is ceramic and can range in size from 1 to 20 millimeters square, based on the ultimate application of the LED. This ceramic base is coated in a metal—usually gold—that allows for a current to flow through the chip and excite the electrons to create light.
Different semiconducting materials emit different colors of light. The color that an LED produces depends on the wavelength of light that the excited electrons emit. Most LEDs initially produce blue light. If manufacturers want another color, they must coat the LED with a chemical layer—typically phosphor—that will convert the blue light to the desired color temperature. Using yellow phosphor will result in white light. The phosphor can be deposited in many ways. For example, manufacturers can coat the semiconductor wafer before it is sliced into chips, or spray the phosphor onto the individual mounted chip.
Direct the Light
The chemical reaction that occurs on the semiconductor generates a point source of light. To make that spot of light usable for a fixture, LED manufacturers need to focus or diffuse that light by adding optical devices, such as a lens, which vary depending on the LED’s ultimate purpose. By adding a lens to the top of the unit, manufacturers can create everything from a tiny pinhole of light for a sensor to a diffused glow for a luminaire.
Click below for a selection of LED products on the market: