High dose Co-60 gamma irradiation of InGaN quantum well light-emitting diodes

InGaN multiquantum-well light-emitting diodes (LEDs) in the form of unpackaged die with emission wavelengths from 410 to 510 nm were irradiated with (60)Co gamma-rays with doses in the range 150-2000 Mrad (Si). The forward turn-on voltage for all the irradiated LEDs was increased slightly (e.g., by only similar to 0.1-0.15 V for 500 MRad dose irradiation) while the reverse breakdown voltage was unchanged within experimental error. The light output intensity for the 410 nm diodes was decreased by 20% after a dose of 150 MRad and 75% after similar to 2 GRad. The current transport in the LEDs was dominated by generation-recombination (ideality factor similar to 2) both before and after irradiation. The morphology and appearance of the p and n-Ohmic metallization did not show any detectable change as a result of even the highest gamma-ray dose