Which factor primarily determines the color of light emitted by a LED?

The color of light emitted by a LED is primarily determined by the material composition of the semiconductor used in the device. Different materials and their specific energy band gaps dictate the wavelength of light that is produced when electrons recombine with holes in the semiconductor. Each material corresponds to a different color of light, ranging from infrared to visible to ultraviolet.

For instance, materials such as gallium arsenide emit infrared light, while gallium phosphide emits green light. The ability to tailor the material allows manufacturers to produce LEDs in various colors, which is a fundamental aspect of LED technology. Other factors, like wattage, voltage, and size, do play roles in the performance and efficiency of LEDs, but they do not intrinsically change the color of light emitted by the LED itself.