Nonradiative carrier capture by point defects in irradiated GaN

In this work, accurate electronic structure calculations are employed to investigate key radiation-relevant defects in gallium nitride, including point defects (vacancies, interstitials, and antisites) as well as the gallium–nitrogen divacancy. Nonradiative carrier capture via multiphonon emission was explored for each of the thermodynamic charge transition levels identified for these defects. Benchmarking was performed using a carbon substitutional defect on a nitrogen site, yielding results that agree well with previous electronic structure and photoluminescence results. Seven defect charge transitions were found to have capture coefficients above 10−10 cm3/s at 300 K: octahedral Gai (+3/+2) electron capture, octahedral Gai (+2/+1) electron capture, tetrahedral Gai (+1/0) electron capture, VN (+1/0) electron capture, VGa (0/+1) hole capture, split Ni (0/−1) electron capture, and VN (0/−1) electron capture. These transitions play a central role in governing defect charge-state populations and the resulting carrier recombination dynamics under irradiation. Previous displacement damage studies found relatively high concentrations of vacancies and nitrogen interstitials; therefore, VGa (0/+1) hole capture, split Ni (0/−1) electron capture, and VN (0/−1) electron capture are likely key contributors to radiation-induced performance degradation in GaN devices.