MeV proton and neutron damage effects on deep-ultraviolet light-emitting diodes

Abstract

270 nm deep-ultraviolet AlGaN light-emitting diodes were irradiated with either neutrons or 15 MeV protons. Neutrons produced via charge-exchange reactions of 9Be with protons exhibited energy ranges from 0 to 33 MeV, with an average energy of approximately 9.8 MeV. The fluences ranged from 1.1 × 1014 to 2.2 × 1014 neutrons cm−2 and 1013 or 1014 protons cm−2. Two primary degradation modes were observed: increased trap-assisted tunneling, indicated by an initial reduction in turn-on voltage, and a decrease in carrier concentration, shown by reduced forward current due to deep state formation. For instance, 15 MeV proton irradiation resulted in more than an order of magnitude reduction in reverse current at a fluence of 1014 ions cm−2. The decrease in subthreshold leakage current at higher fluences of neutrons and protons is attributed to defect-induced carrier trapping, thereby reducing layer conductivity across the p-n junction. Emission intensity decreased with fluence for both protons and neutrons, without a measurable increase in midgap emission. The nonlinear degradation in current and light output with fluence suggests strong dynamic recombination of defects during irradiation of high aluminum alloys.