Abstract
Defect physics of europium (Eu) doped GaN is investigated using first-principles hybrid density-functional defect calculations. This includes the interaction between the rare-earth dopant and native point defects (Ga and N vacancies) and other impurities (O, Si, C, H, and Mg) unintentionally present or intentionally incorporated into the host material. While the trivalent ion is often found to be predominant when Eu is incorporated at the Ga site in wurtzite GaN, the divalent is also stable and found to be predominant in a small range of Fermi-level values in the band-gap region. The / ratio can be tuned by tuning the position of the Fermi level and through defect association. We find co-doping with oxygen can facilitate the incorporation of Eu into the lattice. The unassociated is an electrically and optically active defect center and its behavior is profoundly impacted by local defect-defect interaction. Defect complexes such as , , , , and can efficiently act as deep carrier traps and mediate energy transfer from the host into the -electron core which then leads to sharp red intra- luminescence. Eu-related defects can also give rise to defect-to-band luminescence. The unassociated , for example, is identified as a possible source of the broad blue emission observed in -type, -containing GaN. This work calls for a re-assessment of certain assumptions regarding specific defect configurations previously made for Eu-doped GaN and further investigation into the origin of the photoluminescence hysteresis observed in (Eu,Mg)-doped samples.
4 More- Received 9 September 2020
- Accepted 24 February 2021
DOI:https://doi.org/10.1103/PhysRevMaterials.5.034601
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