Formation and control of the $$E_\mathrm{2}^\mathrm{*}$$ center in implanted β-Ga$$_\mathrm{2}$$O$$_\mathrm{3}$$ by reverse-bias and zero-bias annealing

Journal Article · 20 August 2020 · Journal of Physics. D, Applied Physics

DOI: https://doi.org/10.1088/1361-6463/aba64d · OSTI ID:1651156

Zimmermann, C.  ^[1]; Førdestrøm Verhoeven, E. ^[1]; Kalmann Frodason, Y. ^[1]; Weiser, P. M. ^[1]; Varley, J. B. ^[2]; Vines, L.  ^[1]

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

In this study, deep-level transient spectroscopy measurements are conducted on β-Ga$$_\mathrm{2}$$O$$_\mathrm{3}$$ thin-films implanted with helium and hydrogen (H) to study the formation of the defect level $$E_\mathrm{2}^\mathrm{*}$$ ($$E_\mathrm{A}$$ = 0.71 eV) during heat treatments under an applied reverse-bias voltage (reverse-bias annealing). The formation of $$E_\mathrm{2}^\mathrm{*}$$ during reverse-bias annealing is a thermally-activated process exhibiting an activation energy of around 1.0 eV to 1.3 eV, and applying larger reverse-bias voltages during the heat treatment results in a larger concentration of $$E_\mathrm{2}^\mathrm{*}$$. In contrast, heat treatments without an applied reverse-bias voltage (zero-bias annealing) can be used to decrease the $$E_\mathrm{2}^\mathrm{*}$$ concentration. The removal of $$E_\mathrm{2}^\mathrm{*}$$ is more pronounced if zero-bias anneals are performed in the presence of H. A scenario for the formation of $$E_\mathrm{2}^\mathrm{*}$$ is proposed, where the main effect of reverse-bias annealing is an effective change in the Fermi-level position within the space-charge region, and where $$E_\mathrm{2}^\mathrm{*}$$ is related to a defect complex involving intrinsic defects that exhibits several different configurations whose relative formation energies depend on the Fermi-level position. One of these configurations gives rise to $$E_\mathrm{2}^\mathrm{*}$$, and is more likely to form if the Fermi-level position is further away from the conduction band edge. The defect complex related to $$E_\mathrm{2}^\mathrm{*}$$ can become hydrogenated, and the corresponding hydrogenated complex is likely to form when the Fermi level is close to the conduction band edge. Di-vacancy defects formed by oxygen and gallium vacancies (V$$_\mathrm{O}$$–V$$_\mathrm{Ga}$$) fulfill several of these requirements, and are proposed as potential candidates for $$E_\mathrm{2}^\mathrm{*}$$.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office; Research Council of Norway
• Grant/Contract Number: AC52-07NA27344; 251131
• OSTI ID: 1651156
• Alternate ID(s): OSTI ID: 1651157; OSTI ID: 1668491
• Report Number(s): LLNL-JRNL-812673; 1020090
• Journal Information: Journal of Physics. D, Applied Physics, Vol. 53, Issue 46; ISSN 0022-3727
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English