Influence of doping on the reliability of AlGaInP LEDs

The aging behavior of red-orange AlGaInP light-emitting diodes (LEDs) is investigated. It is found that the amount of magnesium and tellurium doping as well as of the oxygen incorporation influence the device degradation. The generation of non-radiative recombination centers in the active layer is responsible for the decrease of the LED light output during operation. The kinetics of the light aging as well as the configuration of the non-radiative recombination centers emerging during degradation depend on the doping species. High stress temperatures can accelerate the device degradation. For the aging of Te-rich device, the activation energy of 660 meV for the degradation process is determined. Deep level transient spectroscopy is used to investigate the properties of the non-radiative recombination centers. Four deep traps are detected in aged devices. One trap with activation energy of about 1 eV is found in all aged devices. In the aged O-rich device, one additional deep trap is observed with slightly lower activation energy. In the aged Te-rich device two additional shallower traps emerge during degradation.