Cation vacancies as compensating acceptors in (Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> and (In<sub>x</sub>Al<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> alloys
ORAL · Invited
Abstract
Ga2O3 is among the most studied ultra-wide-bandgap materials for developing the next generation of power devices and solar-blind photodetectors. Many of these applications require the formation of heterostructures between Ga2O3 and another material, such as an (AlxGa1-x)2O3 alloy, which provides a conduction-band offset and enables charge carrier confinement. However, these alloys can be difficult to intentionally n-type dope, with a large reduction in charge carriers occurring in Si doped (AlxGa1-x)2O3, even at relatively low Al content.
This is likely due to cation vacancies acting as compensating acceptors, as vacancy defects are abundant in Ga2O3 and can bind up to three electrons. Using Density Functional Theory (DFT) with hybrid functionals, we investigated Al and Ga vacancies in monoclinic Al2O3 and AlGaO3. We predict a critical Al content in AlGaO at which cation vacancies will completely compensate Si doping by comparing the formation energies of the vacancies to that of a Si donor. Our calculations show that such compensation occurs for alloys with 16% Al content or greater, providing insight into existing experimental results.
We propose (InxAl1-x)2O3 as a new and better heterostructure material for β-Ga2O3. Previously we found that (In0.25Al0.75)2O3 has a close lattice match to Ga2O3, while still providing a conduction-band offset [1]. Additionally, we showed that this alloy is theoretically n-type dopable with Si [2]. By investigating cation vacancies in monoclinic In2O3 and InAlO3, we predict that vacancy compensation will be somewhat mitigated in these alloys, with n-type doping predicted to be completely compensated in alloys with 60% Al content or higher. This makes (InxAl1-x)2O3 alloys a promising alternative for β-Ga2O3 heterostructures.
This work was performed in collaboration with H. Peelaers from The University of Kansas.
[1] S. Seacat et al., Phys. Rev. Materials 8, 014601 (2024).
[2] S. Seacat et al., Journal of Applied Physics 135, 235705 (2024).
This is likely due to cation vacancies acting as compensating acceptors, as vacancy defects are abundant in Ga2O3 and can bind up to three electrons. Using Density Functional Theory (DFT) with hybrid functionals, we investigated Al and Ga vacancies in monoclinic Al2O3 and AlGaO3. We predict a critical Al content in AlGaO at which cation vacancies will completely compensate Si doping by comparing the formation energies of the vacancies to that of a Si donor. Our calculations show that such compensation occurs for alloys with 16% Al content or greater, providing insight into existing experimental results.
We propose (InxAl1-x)2O3 as a new and better heterostructure material for β-Ga2O3. Previously we found that (In0.25Al0.75)2O3 has a close lattice match to Ga2O3, while still providing a conduction-band offset [1]. Additionally, we showed that this alloy is theoretically n-type dopable with Si [2]. By investigating cation vacancies in monoclinic In2O3 and InAlO3, we predict that vacancy compensation will be somewhat mitigated in these alloys, with n-type doping predicted to be completely compensated in alloys with 60% Al content or higher. This makes (InxAl1-x)2O3 alloys a promising alternative for β-Ga2O3 heterostructures.
This work was performed in collaboration with H. Peelaers from The University of Kansas.
[1] S. Seacat et al., Phys. Rev. Materials 8, 014601 (2024).
[2] S. Seacat et al., Journal of Applied Physics 135, 235705 (2024).
*Funding provided by NSF grant DMR-2425549 (FuSe2).
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Publication: S. Seacat et al., 'Investigating compensation from cation vacancies in Si doped
monoclinic (AlxGa1−x)2O3 alloys' (in preparation).
S. Seacat et al., 'Achieving n-type doped monoclinic (InxAl1-x)2O3 alloys', Journal of Applied Physics 135, 235705 (2024).
S. Seacat et al., 'Computational design of optimal heterostructures β-Ga2O3', Phys. Rev. Materials 8, 014601 (2024).
Presenters
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Sierra Caitlin Seacat
- University of Kansas