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DOE OSTI · 3020842

Evidence for Ga clusters in β-Ga 2 O 3 from Raman spectroscopy and density functional theory

Huso, Jesse [Klar Scientific, Pullman, WA (United States)] (ORCID:000000028894967X)·Dutton, Benjamin [Washington State Univ., Pullman, WA (United States)] (ORCID:000000031272130X)·Remple, Cassandra [Washington State Univ., Pullman, WA (United States)] (ORCID:0000000172831696)·McCluskey, Matthew D. [Klar Scientific, Pullman, WA (United States); Washington State Univ., Pullman, WA (United States)] (ORCID:0000000207864106)·McCloy, John S. [Washington State Univ., Pullman, WA (United States)] (ORCID:0000000174767771)·Bhattacharyya, Arkka [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000272095681)·Krishnamoorthy, Sriram [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000246821002)·Rebollo, Steve [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000198068924)·Speck, James S. [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000280454090)·Varley, Joel B. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000253845248)·Voss, Lars F. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000263498219)
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Abstract

Monoclinic gallium oxide (β-Ga 2 O 3 ) single crystals have a Raman mode at ∼250 cm −1 that is strongly correlated with free-electron density. Prior work attributed this peak to an electronic excitation of a shallow donor impurity band. However, heavily n-type thin films grown by metalorganic chemical vapor deposition or molecular beam epitaxy do not have the peak. In the present work, an alternate model is proposed: the 250 cm −1 Raman peak arises from Ga clusters, defined as two or more Ga atoms that form Ga–Ga bonds. Raman mapping reveals variations in the frequency that are consistent with a distribution of cluster sizes. The intensity of the peak decreases as the temperature is raised, attributed to melting of the Ga clusters. First-principles calculations indicate that the 250 cm −1 mode is due to Ga–Ga bond-stretching vibrations. As the Fermi energy is raised, the formation of Ga–Ga dimers becomes energetically favorable, explaining the correlation between n-type conductivity and the appearance of the Raman peak.

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36 MATERIALS SCIENCEDensity functional theoryDopingElectronic excitationEpitaxyFirst-principle calculationsMaterials scienceOxidesPhononsRaman spectroscopySemiconductor device fabricationThin films

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Huso, Jesse [Klar Scientific, Pullman, WA (United States)] (ORCID:000000028894967X), Dutton, Benjamin [Washington State Univ., Pullman, WA (United States)] (ORCID:000000031272130X), Remple, Cassandra [Washington State Univ., Pullman, WA (United States)] (ORCID:0000000172831696), McCluskey, Matthew D. [Klar Scientific, Pullman, WA (United States); Washington State Univ., Pullman, WA (United States)] (ORCID:0000000207864106), McCloy, John S. [Washington State Univ., Pullman, WA (United States)] (ORCID:0000000174767771), Bhattacharyya, Arkka [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000272095681), Krishnamoorthy, Sriram [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000246821002), Rebollo, Steve [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000198068924), Speck, James S. [Univ. of California, Santa Barbara, CA (United States)] (ORCID:0000000280454090), Varley, Joel B. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000253845248), Voss, Lars F. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000263498219). 2025-10-03. Evidence for Ga clusters in β-Ga 2 O 3 from Raman spectroscopy and density functional theory. https://doi.org/10.1063/5.0292434

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36 MATERIALS SCIENCE↗