Modulation of thermal conductivity of iron-doped β-Ga₂O₃ by helium-ion irradiation

β-Ga₂O₃ is an important ultra-wide bandgap oxide semiconductor that has recently gained significant attention in radiation detection. This study examined the impact of helium-ion irradiation on the anisotropic thermal conductivity of iron-doped β-Ga₂O₃. A laser-based spatial domain thermoreflectance technique was used to measure the thermal conductivity map, which was validated against simulation results derived from density functional theory-based phonon transport simulations. Our experimental results revealed that the irradiation damage led to 40 % reduction in the thermal conductivity along [001] direction and 25 % along [100] directions, which significantly reduced the anisotropy of thermal conductivity. Phonon transport simulations indicated that the thermal conductivity decreases when helium atom is at interstitial sites or vacancy sites, and such reduction is particularly evident when helium atom occupies vacancy sites. This work underscores the role of irradiation-induced microstructural changes in the thermal transport properties of β-Ga₂O₃, which is crucial for its applications in sensor devices for extreme environments.