Diffusion of acceptor dopants in monoclinic 𝛽−Ga_2⁢O₃

Journal Article · Mon Sep 29 00:00:00 EDT 2025 · Physical Review Materials

DOI:https://doi.org/10.1103/6dpb-ctf2· OSTI ID:3009944

Lee, Channyung ^[1]; Scarpulla, Michael A. ^[2]; Ertekin, Elif ^[1]; Varley, Joel B. ^[3]

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1. Univ. of Illinois at Urbana-Champaign, IL (United States)
2. Univ. of Utah, Salt Lake City, UT (United States)
3. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

𝛽−Ga₂⁢O₃ is a promising material for next-generation power electronics because of its ultrawide band gap and high critical breakdown voltage. However, realizing its full potential requires precise control over dopant incorporation and stability. In this work, we use first-principles calculations to systematically assess the diffusion behavior of eight potential deep-level substitutional acceptors (Au, Ca, Co, Cu, Fe, Mg, Mn, and Ni) in 𝛽−Ga₂⁢O₃. We consider two key diffusion mechanisms: (i) interstitial diffusion under nonequilibrium conditions relevant to ion implantation, and (ii) trap-limited diffusion (TLD) under near-equilibrium thermal annealing conditions. Our results reveal a strong diffusion anisotropy along the 𝑏 and 𝑐 axes, with dopant behavior governed by competition between diffusion and incorporation (or dissociation) activation energies. Under interstitial diffusion, Ca$$^{2+}_{i}$$ and Mg$$^{2+}_{i}$$ show the most favorable combination of low migration and incorporation barriers, making them promising candidates for efficient doping along the 𝑏 and 𝑐 axes, respectively. In contrast, Au$$^{+}_{i}$$ diffuses readily, but exhibits an incorporation barrier that exceeds 5 eV, rendering it ineffective as a dopant. From a thermal stability perspective, Co$$^{2+}_{i}$$ shows poor activation but high diffusion barriers, which may suppress undesirable migration at elevated temperatures. Under trap-limited diffusion, the dissociation of dopant-host complexes controls mobility. Mg$$^{2+}_{i}$$ again emerges as a leading candidate, exhibiting the lowest dissociation barriers along both axes, whereas Co$$^{2+}_{i}$$ and Fe$$^{2+}_{i}$$ display the highest barriers, suggesting improved dopant retention under thermal stress. In conclusion, our findings guide dopant selection by balancing activation and thermal stability, essential for robust semi-insulating substrates.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR); USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Materials & Manufacturing Technologies Office (AMMTO)
• Grant/Contract Number: AC52-07NA27344; NA0004153
• OSTI ID: 3009944
• Report Number(s): LLNL--JRNL-2010980
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 9 Vol. 9; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

Defects
Density functional theory
Diffusion
First-principles calculations
Materials science
Semiconductors
Wide band gap systems