265 nm AlGaN-based deep-ultraviolet light-emitting diodes grown on AlN substrates studied by photoluminescence spectroscopy under ideal pulsed selective and non-selective excitation conditions

Photoluminescence (PL) spectroscopy under ideal pulsed selective and non-selective excitation conditions is used to study 265 nm AlGaN-based light-emitting diodes grown on AlN substrates. Excitation-power-density-dependent PL measurements under selective excitation conditions show that the internal quantum efficiency of the quantum-well layers is unity at cryogenic temperatures under weak excitation regime. Temperature-dependent and time-resolved PL measurements demonstrate the high internal quantum efficiency at room temperature. The PL thermal quenching behaviors differ under the two excitation conditions, indicating a nonradiative recombination process at the quantum-barrier layers. We propose that the nonradiative recombination process is a limiting factor of the external quantum efficiency.