Origin of the redshift of the luminescence peak in InGaN light-emitting diodes exposed to Co-60 γ-ray irradiation

The redshift (∼54 meV) of the photoluminescence (PL) peak energy of blue InGaN/GaN light-emitting diodes exposed to 60Co γ-rays was observed. Time-resolved PL indicates that the PL radiative time increases along with irradiation does. The temperature-dependent PL and photoreflectance techniques show that γ-ray irradiance leads to higher carrier localization energies and larger Stokes' shift, respectively. These facts suggest that the redshifts of the PL peak emission introduced by γ-ray irradiance mainly originated from the enhancement of indium fluctuation. The cathodoluminescent images of the samples before and after γ-ray irradiation are compared to verify the results.