Achieving n-type doped monoclinic (In_xAl_1-x)₂O₃ alloys

Ga₂O₃ is an ultrawide-bandgap oxide with potential applications for power devices and solar-blind photodetectors. The formation of heterostructures between Ga₂O₃ and another material, typically AlGaO, is necessary to realize the full potential of Ga₂O₃-based devices. However, the smaller lattice constants of Al₂O₃ introduce strain to these heterostructures, resulting in lower quality materials. Previously, we proposed the monoclinic (In_0.25Al_0.75)₂O₃ alloy as an ideal material to create monoclinic Ga₂O₃ heterostructures, as it provides a close lattice match to β-Ga₂O₃ along with a 1 eV conduction-band offset [1].

Achieving intentional n-type doping in this alloy is required for it to be used in heterostructures with Ga₂O₃. Here, we use density functional theory with hybrid functionals to investigate common donor dopants, such as Si, Sn, C, and Ge substituting on cation sites, and H interstitials, in monoclinic In₂O₃ and InAlO₃. We identify Si as the optimal donor, as it is shallow for In concentrations above 14%. These donors also have a low formation energy, indicating that they will incorporate during growth. For higher In concentrations, Sn (above 33% In) and Ge (above 35% In) are also promising donors, with Sn having comparable formation energies to Si [2].

[1] S. Seacat et al., Phys. Rev. Materials 8, 014601 (2024).

[2] S. Seacat et al., Journal of Applied Physics 135, 235705 (2024).