The exact cause of drooping photon production in nitride-based LEDs has been hotly debated between two main camps: One thinks the electrons become so energized that they overflow the quantum well and escape. The other camp, to which Van de Walle's group belongs, thinks that the energy created by an electron/hole combination -- physicists call it "recombination" -- is being quietly swallowed by another charge carrier (a hole or an electron) inside the quantum well. This phenomenon is called Auger recombination.
In the case of blue and green LEDs, the base semiconductor material is gallium nitride, so the entire family is called nitride-based LEDs.
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