Title: Multistability of isolated and hydrogenated Ga–O divacancies in β–Ga₂O₃

Abstract

This work systematically explores 19 unique configurations of the close-associate Ga–O divacancies (V_GaV_O) in β–Ga₂O₃, including their complexes with H impurities, using hybrid functional calculations. Interestingly, most configurations are found to retain the negative-U behavior of V_O, as they exhibit a thermodynamic (–/3–) charge-state transition level energetically located in the upper part of the band gap, where the 3– charge state is associated with the formation of a Ga–Ga dimer. The energy positions of the thermodynamic (–/3–) charge-state transition levels divide the divacancy configurations into three different groups, which can be understood from the three possible Ga–Ga dimerizations resulting from the tetrahedral and octahedral Ga sites. The relative formation energies of the different divacancy configurations, and hence the electrical activity of the divacancies, is found to depend on the Fermi-level position, and the energy barriers for transformation between different divacancy configurations are explored from nudged elastic band calculations. Hydrogenation of the divacancies is found to either passivate their negative-U charge-state transition levels or shift them down in Fermi level position, depending on whether the H resides at V_O or forms an O–H bond at V_Ga, respectively. Finally, the divacancy is discussed as a potential origin of the so-called E$$^{*}_{2}$$ center previously observed by deep-level transient spectroscopy.

Authors:

Frodason, Y. K. ^[1]; Zimmermann, C.  ^[1];

• Search DOE PAGES for author "Zimmermann, C."
• Search DOE PAGES for ORCID "0000-0003-3708-6074"

Verhoeven, E. F. ^[1]; Weiser, P. M.  ^[1];

• Search DOE PAGES for author "Weiser, P. M."
• Search DOE PAGES for ORCID "0000-0003-1009-9940"

Vines, L. ^[1]; Varley, J. B. ^[2]

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+ Show Author Affiliations

1. Univ. of Oslo (Norway)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Wed Feb 03 00:00:00 EST 2021

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office

OSTI Identifier:

1828655

Report Number(s):

LLNL-JRNL-814947
Journal ID: ISSN 2475-9953; 1023918; TRN: US2216820

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review Materials

Additional Journal Information:

Journal Volume: 5; Journal Issue: 2; Journal ID: ISSN 2475-9953

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Electronic structure; Point defects; Semiconductor compounds; Transparent conducting oxides; Wide band gap systems; Density functional calculations; Hybrid functionals