Mechanisms leading to thermal quantum efficiency droop in green InGaN/GaN LEDs

The contribution of several mechanisms into the external quantum efficiency (EQE) droop in green InGaN/GaN LEDs over a temperature increase from 300 to 400 K is clarified. One of them is the ionization of atoms localized at disordered hetero-interfaces in InGaN/GaN MQWs situated at the depletion region around a p-n junction at j < 10 A/cm² and U < U_tr (turn on voltage). The ionized atoms capture tunneling charge carriers, which leads to EQE decrease. Another mechanism is the capture of charge carriers tunneling in 3D spaces of MQWs situated outside of a depletion region at U > U_tr and 10 A/cm² < j < 30 A/cm². Growing thermalized carriers concentration reduces the band fluctuation potential which results in vertical diffusion transport of carriers and crowding effect.