LED stands for Light Emitting Diode. Ok…..so what does that really mean?
LED lighting is part of a lighting group called Solid State Lighting. Solid State Lighting includes both LED and OLED (Organic Light Emitting Diode). LED based lights are small light sources that become illuminated by the movement of electrons through a semiconductor material.
The LED light starts with a tiny chip very small about one millimeter or the size of a piece of pepper. The chip is comprised of layers of semi-conducting material. LED packages may contain one chip or multiple chips and are mounted on a heat conducting material called a heat sink and they usually have an enclosed lens.
LED diodes, in general, are made of very thin layers of semiconductor material; one layer will have an excess of electrons, while the next will have a deficit of electrons. This difference causes electrons to move from one layer to another, thereby generating light. Manufacturers can now make these layers as thin as .5 micron or less (1 micron = 1 ten-thousandth of an inch). Impurities within the semiconductor are used to create the required electron density. A semiconductor is a crystalline material that conducts electricity only when there is a high density of impurities in it. The slice, or wafer, of semiconductor is a single uniform crystal, and the impurities are introduced later during the manufacturing process. Think of the wafer as a cake that is mixed and baked in a prescribed manner, and impurities as nuts suspended in the cake. The particular semiconductors used for LED manufacture are gallium arsenide (GaAs), gallium phosphide (GaP), or gallium arsenide phosphide (GaAsP). The different semiconductor materials (called substrates) and different impurities result in different colors of light from the LED.
How LED create white light
The graph below represents three different ways to create white light when designing LED’s. The most prevalent in today’s modern LED’s is the first option (Phosphor Conversion) a process where a blue gallium nitride diode excites a yellow emitting phosphor. The result of mixing blue and yellow creates a white light. By changing or varying the yellow phosphor it changes the color of white to either a warmer light or cooler light. By design LED light provides a high level of blue light.