Low cross-plane thermal conductivity of κ-Ga2O3 thin films
Abstract
The thermal conductivities of (001) κ-Ga2O3 thin films deposited on c-plane sapphire substrates were measured with frequency-domain thermoreflectance (FDTR). The thermal conductivity increases from 1.83 +0.19−0.18 W/m·K to 2.26 +0.35−0.40 W/m·K as the thicknesses increase from 159 nm to 689 nm. This weak thickness dependence indicates that the majority of the intrinsic phonon mean free paths are smaller than the range of investigated film thicknesses. First-principles-based calculations that include phonon-phonon and phonon-boundary scattering capture this size-dependent behavior and support our experimental observation. Temperature-dependent measurements of a 689 nm film from 293 to 400 K show a decrease in thermal conductivity with increasing temperature due to enhanced phonon-phonon scattering. A weaker temperature dependence is observed in a 159 nm film where phonon-boundary scattering becomes more prominent. At comparable film thicknesses, our measured κ-Ga2O3 films exhibit lower values of cross-plane thermal conductivity than the other experimentally measured Ga2O3 polymorphs. Our experimental observations are supported by prior predictions, which suggest that the low thermal conductivity of κ-Ga2O3 results from its complex crystal structure, which leads to increased anharmonicity and lower phonon group velocities relative to other polymorphs. Thermal management strategies, such as integration with high-thermal-conductivity substrates, may thus be required to mitigate self-heating for κ-Ga2O3-based electronic devices.
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BibTeX
@misc{park2026crossplane,
title = {{Low cross-plane thermal conductivity of $κ$-Ga$_2$O$_3$ thin films}},
author = {Seungwon Park and Jingyu Tang and Minsung An and Alan J. H. McGaughey and Lisa M. Porter and Robert F. Davis and Jonathan A. Malen},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05647},
eprint = {2611.05647},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05647},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Low cross-plane thermal conductivity of κ-Ga_2O_3 thin films
AU - Seungwon Park
AU - Jingyu Tang
AU - Minsung An
AU - Alan J. H. McGaughey
AU - Lisa M. Porter
AU - Robert F. Davis
AU - Jonathan A. Malen
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05647
UR - https://arxiv.org/abs/2611.05647
AB - The thermal conductivities of (001) κ-Ga_2O_3 thin films deposited on c-plane sapphire substrates were measured with frequency-domain thermoreflectance (FDTR). The thermal conductivity increases from 1.83 ^+0.19_−0.18 W/m·K to 2.26 ^+0.35_−0.40 W/m·K as the thicknesses increase from 159 nm to 689 nm. This weak thickness dependence indicates that the majority of the intrinsic phonon mean free paths are smaller than the range of investigated film thicknesses. First-principles-based calculations that include phonon-phonon and phonon-boundary scattering capture this size-dependent behavior and support our experimental observation. Temperature-dependent measurements of a 689 nm film from 293 to 400 K show a decrease in thermal conductivity with increasing temperature due to enhanced phonon-phonon scattering. A weaker temperature dependence is observed in a 159 nm film where phonon-boundary scattering becomes more prominent. At comparable film thicknesses, our measured κ-Ga_2O_3 films exhibit lower values of cross-plane thermal conductivity than the other experimentally measured Ga_2O_3 polymorphs. Our experimental observations are supported by prior predictions, which suggest that the low thermal conductivity of κ-Ga_2O_3 results from its complex crystal structure, which leads to increased anharmonicity and lower phonon group velocities relative to other polymorphs. Thermal management strategies, such as integration with high-thermal-conductivity substrates, may thus be required to mitigate self-heating for κ-Ga_2O_3-based electronic devices.
ER -