Proton-irradiation-induced degradation in GaN-based UV LEDs: Role of unintentionally doped carbon

Degradation and defect evolution in GaN-based UV LEDs under 3 MeV proton irradiation were throughly investigated in this work. Combined with the yellow luminescence band at similar to 2.2 eV in photoluminescence spectra with the energy level of E-v + 0.16 eV extracted by deep-level transient spectroscopy measurement, an intrinsic C-N-related defect with an abnormally decreased concentration after irradiation was identified. Based on energy levels, the spatial configuration of defects, and their correlations, several possible origins and evolution processes of the defects are systematically discussed. A defect evolution model under proton irradiation was established: C atoms departed from the C-N-related defect aligned along the dislocation in the active region stimulated by the displacement damage effect, leaving behind a nitrogen vacancy (V-N) aligned along the dislocation, accompanied by the generation of a non-interacting carbon interstitial (C-i). Both the increased V-N and C-i were found to contribute jointly to the decrease in optical power and the increase in leakage current. This indicates that carbon-a common unintentional dopant in GaN-based optical devices-can be an important factor in the degradation of GaN-based UV LEDs under proton irradiation, and should be further noted in radiation resistance applications.

Automated summary

Degradation and defect evolution in GaN-based UV LEDs under 3 MeV proton irradiation were investigated thoroughly in this study. An intrinsic C-N-related defect with an abnormally decreased concentration after irradiation was identified. A defect evolution model under proton irradiation was established: C atoms departed from the C-N-related defect aligned along the dislocation in the active region stimulated by the displacement damage effect, leaving behind a nitrogen vacancy (V-N) aligned along the dislocation, accompanied by the generation of a non-interacting carbon interstitial (C-i). The increase in V-N and C-i jointly contributed to the decrease in optical power and the increase in leakage current.