Theory of magnetic 3 d transition metal dopants in gallium nitride

Journal Article · 11 May 2023 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.107.205202 · OSTI ID:1973280

Schultz, Peter A.  ^[1]; Edwards, Arthur H. ^[2]; Van Ginhoven, Renee M. ^[2]; Hjalmarson, Harold P. ^[1]; Mounce, Andrew M. ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2. Air Force Research Lab. (AFRL), Kirtland Air Force Base, NM (United States)

Using first-principles density functional theory (DFT) methods and size-converged supercell models, we analyze the electronic and atomic structure of magnetic $3d$ transition metal dopants in cubic gallium nitride (c-GaN). All stable defect charge states for Fermi levels across the full experimental gap are computed using a method that correctly resolves the boundary condition problem (without a jellium approximation) and eliminates finite-size errors. The resulting computed defect levels are not impacted by the DFT band-gap problem, they span a width consistent with the experimental gap rather than being limited to the single-particle DFT gap. All defects with electronically degenerate (half-metal) $$T$$_d ground states are found to have significant distortions, relaxing to $$D$$_2d structures driven by the Jahn-Teller instability. This leads to insulating ground states for all substitutional $3d$ dopants, refuting claims in the literature that +$$U$$ or hybrid functional methods are required to avoid artificial half-metal results. Interpreting the $$d$$ⁿ atomic occupations within a crystal-field model and exchange splittings, we identify a systematic trend across the $3d$ transition metal series. Approaches to estimate excited-state energies as observed in photoluminescence from defect centers are assessed, ranging from a Koopmans-type single-particle energy interpretation to relaxed total energy differences in fully self-consistent DFT. The single-particle interpretations are found to be qualitatively predictive and the calculations are consistent with the limited available experimental data across the $$3$$d dopant series. These results provide a baseline understanding to guide future studies and a conceptual framework within which to interpret new results.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies (CINT)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC); USDOE Advanced Research Projects Agency - Energy (ARPA-E); US Air Force Office of Scientific Research (AFOSR)
• Grant/Contract Number: NA0003525; FA9550-17RVCOR505; FA9550-21RVCOR503; 218242
• OSTI ID: 1973280
• Alternate ID(s): OSTI ID: 2311441
• Report Number(s): SAND-2023-04360J; TRN: US2409149
• Journal Information: Physical Review. B, Vol. 107, Issue 20; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English