Oxygen is the most common unintentional impurity found in GaN. We study the interaction between substitutional oxygen (ON) and the gallium vacancy (VGa) to form a point defect complex in GaN. The formation energy of the gallium vacancy is largely reduced in n-type GaN by complexing with oxygen, while thermodynamic and optical transition levels remain within the band gap. We study the spectroscopy of this complex using a hybrid quantum-mechanical molecular-mechanical (QM/MM) embedded-crystal approach. We reveal how a single defect center can be responsible for multiband luminescence, including the ubiquitous yellow luminescence signature observed in n-type GaN, owing to the coexistence of diffuse (extended) and compact (localized) holes.
@article{arxiv.1802.10222,
title = {Assignment of multiband luminescence due to the gallium vacancy-oxygen defect complex in GaN},
author = {Zijuan Xie and Yu Sui and John Buckeridge and Alexey A. Sokol and Thomas W. Keal and Aron Walsh},
journal= {arXiv preprint arXiv:1802.10222},
year = {2018}
}