LEDs emit light when forward biased, and when voltage is applied across the junction to forward bias it, current flows as if it were in the case of any PN junction. Holes from the p-type region and electrons from the n-type region enter the junction and recombine like a normal diode to flow current. When this happens, energy is released, some of which comes in the form of photons.

Most of the light was found to be generated from the junction region near the P-type region. Therefore, the diode is designed so that the region is as close as possible to the surface of the device to ensure that the minimum amount of light absorbed in the structure is achieved.