The efficacy expressed in terms of this ultimate measurable visible energy is called the external efficacy. The high index of refraction of most semiconductors causes the light to reflect back from the surface into the crystal and highly attenuated before finally exiting. The efficacy depends on the light energy generated at the junction and losses due to re-absorption when light tries to escape through the crystal. The luminous efficacies of typical AlInGaP LEDs and InGaN LEDs for different peak wavelengths are shown in the table below.
Photon emission occurs due to electron-hole recombination in the p-region.Įlectron energy transitions across the energy gap, called radiative recombinations, produce photons (i.e., light), while shunt energy transitions, called non-radiative recombinations, produce phonons (i.e., heat). When the forward biased current I F is applied through the p-n junction of the diode, minority carrier electrons are injected into the p-region and corresponding minority carrier electrons are injected into the n-region.
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