Point defects controlling non-radiative recombination in GaN blue light emitting diodes: Insights from radiation damage experiments

The role of Shockley-Read-Hall non-radiative recombination centers on electroluminescence (EL) efficiency in blue multi-quantum-well (MQW) 436 nm GaN/InGaN light emitting diodes (LEDs) was examined by controlled introduction of point defects through 6 MeV electron irradiation. The decrease in the EL efficiency in LEDs subjected to irradiation with fluences above 5 × 10 ¹⁵ cm ^-2 was closely correlated to the increase in concentration of E _c -0.7 eV electron traps in the active MQW region. This increase in trap density was accompanied by an increase in the both diode series resistance and ideality factor (from 1.4 before irradiation to 2.1 after irradiation), as well as the forward leakage current at low forward voltages that compromise the injection efficiency. Hole traps present in the blue LEDs do not have a significant effect on EL changes with radiation because of their low concentration.