Electron paramagnetic resonance centers and defects in β-Ga₂O₃

β-Ga₂O₃ has a wide band gap (4.7 eV) and doped semiconducting properties, making the material attractive for high-power electronics applications. However, the understanding of the material’s defect physics remains incomprehensive.

Skachkov et al. reported findings on electron paramagnetic resonance (EPR) centers in irradiated β-Ga₂O₃. Using density functional theory calculations of the magnetic resonance fingerprint (g-tensor and hyperfine interaction), they developed models to identify the EPR centers in β-Ga₂O₃ semiconductor with specific defect configurations.

The low symmetry of the β-Ga₂O₃ crystal, which contains tetrahedral- and octahedral-coordinated gallium and three different oxygen sites, makes the task of associating an EPR spectrum with a defect more complicated than usual. The researchers calculated gyromagnetic g-tensor and hyperfine parameters using a wide range of models and found the ones that agreed with their experimental data: the EPR1 center corresponds to a complex of two tetrahedral gallium-vacancies with an interstitial gallium in between with a specific orientation; the EPR2 center, observed only after the crystal have undergone optical excitation, corresponds to an octahedral gallium-vacancy, with a tilted spin density.

Compared with other defect spectroscopies, which tend to focus on energy levels, the combined theory/experiment EPR investigation provides a more detailed look at the defect electronic structure.

The authors believe that their new computational approach can be used for studying defects in other types of semiconductors.

Source: “Computational identification of Ga-vacancy related electron paramagnetic resonance centers in β-Ga₂O₃,” by Dmitry Skachkov, Walter R. L. Lambrecht, Hans Jürgen von Bardeleben, Uwe Gerstmann, Quoc Duy Ho, and Peter Deák, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5092626 .