【Domestic Papers】Jinling Institute of Technology --- Increased thermal conductivity of β-Ga₂O₃ using Al substitution: Full spectrum phonon engineering

      Researchers from the Jinling Institute of Technology have published a dissertation titled "Increased thermal conductivity of β-Ga₂O₃ using Al substitution: Full spectrum phonon engineering" in Journal of Applied Physics.

Acknowledgments

      This work was financially supported by the Science Foundation of Jinling Institute of Technology (No. jit-rcyj-202001) and the scholarship from China Scholarship Council (CSC) under Grant No. 202308320197. Professor Chang is working at the Nanyang Technological University supported by the National Research Foundation, Singapore, under its Fellowship Award (No. NRF-NRFF13-2021-0010), the Agency for Science, Technology and Research (A*STAR) under its Manufacturing, Trade and Connectivity (MTC) Individual Research Grant (IRG) (Grant No. M23M6c0100), the Singapore Ministry of Education (MOE) Academic Research Fund Tier 3 Grant (No. MOE-MOET32023-0003), the Singapore Ministry of Education (MOE) AcRF Tier 2 Grant (No. MOE-T2EP50222-0014), and the Nanyang Assistant Professorship Grant (NTU-SUG).

Background

      Gallium oxide (β-Ga₂O₃) is drawing widespread attention in the field of power electronics primarily due to its ultra-wide bandgap of approximately 4.8–4.9 eV, which is significantly higher than that of GaN (3.4 eV). The ultra-wide bandgap enables β-Ga₂O₃ devices to operate at an exceptionally high critical electric field (∼8 MV/cm), far exceeding GaN (∼3.3 MV/cm). This allows for the fabrication of devices that can sustain higher voltages with smaller geometries, enhancing energy efficiency and reducing size. Besides, β-Ga₂O₃ can be easily deposited using magnetron sputtering in a low vacuum condition without worrying about oxygen, simplifying the process.

Abstract

      Improving the thermal conductivity of β-Ga₂O₃ is critical for optimizing its performance in high-power electronic devices, as effective thermal management significantly influences their output power and reliability. In this work, the thermal conductivities of β-Ga₂O₃ and (Al_xGa_1−x)₂O₃ alloys along the (⁠-201) direction were first computed using a non-equilibrium molecular dynamics method based on the deep learning potential. Our results indicate that the calculated thermal conductivity of β-Ga₂O₃ is 16.6 W m⁻¹K⁻¹ along the (⁠-201) direction, which is in excellent agreement with experimental measurements. In our findings, an Al to Ga ratio of 1:1 leads to the thermal conductivity of the (Al_xGa_1−x)₂O₃ alloy being more than twice that of β-Ga₂O₃, regardless of the Al substitution sites. The (Al_0.5Ga_0.5)₂O₃ alloy exhibits enhanced thermal conductivity due to the improved transport properties of optical phonon modes, including the increased group velocities, the enhanced participation, and the induced new vibrational modes at higher frequencies. This research provides theoretical predictions regarding the optimal Al to Ga ratio to enhance the thermal conductivity of (Al_xGa_1−x)₂O₃ alloys, offering crucial insights for the design and thermal management of β-Ga₂O₃ power devices.

Conclusion

      In conclusion, we conducted numerical training based on deep neural network models to accurately describe the interactions between atoms in β-Ga₂O₃ and (Al_xGa_1−x)₂O₃ alloys. By establishing potential functions that characterize the energy and forces acting on the atoms, we were able to perform the NEMD simulations of thermal conductivities for both β-Ga₂O₃ and (Al_xGa_1−x)₂O₃ alloys along the (⁠-201) direction. Our calculated thermal conductivity for β-Ga₂O₃ is 16.6 W m⁻¹K⁻¹, which aligns well with experimental values.