Computational Prediction of the Intrinsic Point Defects of α-Ga_₂O_₃: Cation Split-Vacancy Configuration

Gallium oxide (Ga₂O₃) is an emerging wide-bandgap semiconductor with significant potential in power electronics and optoelectronics. Among the polymorphs, α-Ga₂O₃ which is isostructural to sapphire exhibits the largest bandgap of around 5.1 to 5.3 eV and a breakdown electric field of 9.5 MV/cm.¹ Research on α-Ga₂O₃ was mainly focused on materials properties and growth, while its point defect chemistry and the influence of defects on its optical properties remain overlooked. With the benefit of having a wide bandgap, extrinsic doping can introduce new energy levels within the bandgap, enhancing the radiative recombination process, and thus improving photoluminescence efficiency.

In this work, we employ PBE0 hybrid Density Functional Theory (DFT) to investigate both the intrinsic defect chemistry, extrinsic defects with Silicon (Si), Tin (Sn) and Germanium (Ge) doping of α-Ga₂O₃ and their corresponding optical transition levels after extrinsic doping. ² We observe a large optical band gap of around 5.60 eV, matching well with the experimental data of 5.61 eV.³ Understanding defects is crucial for determining the optical transition levels as they can introduce new recombination pathways that shift the wavelength of emitted light, which is useful for tuning the photoluminescence properties of a material. Therefore, comprehensive intrinsic and extrinsic defect studies were performed using ShakeNBreak and DOPED,^4–6 and the optical transition levels were also studied, providing valuable insight towards the photoluminescence properties of Si, Sn and Ge-doped α-Ga₂O_3.

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