What do the LED made of?

The main semiconductor materials used to manufacture LEDs are:

Indium gallium nitride (InGaN): blue, green and ultraviolet high-brightness LEDs

Aluminum gallium indium phosphide (AlGaInP): yellow, orange and red high-brightness LEDs

Aluminum gallium arsenide (AlGaAs): red and infrared LEDs

Gallium phosphide (GaP): yellow and green LEDs