When LED is manufactured by using aluminium gallium arsenide (AlGaAs), it emits

The emitted color of an LED corresponds to the band gap energy of its semiconductor material. AlGaAs has a band gap that typically produces infrared radiation when electrons and holes recombine at the p-n junction.

Variations in aluminium composition allow tuning of the band gap, but AlGaAs LEDs predominantly emit in the infrared spectrum, as seen in devices like remote controls and optical communication systems. Other materials such as GaN or InGaN are required for ultraviolet, green, or blue emission.