Computational spectroscopy for point defects in AlN and AlGaN
ORAL
Abstract
This talk presents two examples where first-principles calculations proved crucial for defect identification in AlN and AlGaN.
The first example is on electron-paramagnetic resonance (EPR) measurements of AlN, which have often observed a hyperfine signal (D5) commonly assigned to a donor-like defect. The microscopic origin of this defect has been debated for over two decades. Using first-principles calculations and photo-EPR measurements, we show the D5 defect is actually a deep acceptor, carbon substituting on the nitrogen site, not a deep donor.
The second example focuses on the recent proposal of germanium as a viable n-type dopant for high-Al content AlGaN and AlN. Combining experimental results with theoretical analysis, we demonstrate that above 50% Al composition, germanium behaves as a DX-center in AlGaN, suppressing n-type conductivity. These findings provide important guidance for doping strategies to achieve efficient n-type conductivity in high Al-content AlGaN and AlN.
The first example is on electron-paramagnetic resonance (EPR) measurements of AlN, which have often observed a hyperfine signal (D5) commonly assigned to a donor-like defect. The microscopic origin of this defect has been debated for over two decades. Using first-principles calculations and photo-EPR measurements, we show the D5 defect is actually a deep acceptor, carbon substituting on the nitrogen site, not a deep donor.
The second example focuses on the recent proposal of germanium as a viable n-type dopant for high-Al content AlGaN and AlN. Combining experimental results with theoretical analysis, we demonstrate that above 50% Al composition, germanium behaves as a DX-center in AlGaN, suppressing n-type conductivity. These findings provide important guidance for doping strategies to achieve efficient n-type conductivity in high Al-content AlGaN and AlN.
*Funding acknowledgement: Office of Naval Research through the Naval Research Laboratory's Basic Research Program.
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Publication: [1] D. Wickramaratne, M. Siford, M. S. I. Mollik, J. L. Lyons, and M. E. Zvanut, "Direct evidence for carbon incorporation on the nitrogen site in AlN," Physical Review Materials, vol. 8, no. 9. American Physical Society (APS), Sep. 11, 2024. doi: 10.1103/physrevmaterials.8.094602.
[2] J. Forbus, D. Wickramaratne, J. L. Lyons, and M. E. Zvanut, "Nonradiative quenching of EPR signals in germanium-doped AlGaN: Evidence for DX-center formation," Applied Physics Letters, vol. 126, no. 4. AIP Publishing, Jan. 27, 2025. doi: 10.1063/5.0249701
Presenters
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Darshana Wickramaratne
- United States Naval Research Laboratory