High thermal conductivity of rutile-GeO2 film by metal-organic chemical vapor deposition: 52.9 W m−1 K−1

Rutile germanium dioxide (r-GeO2) has recently emerged as a promising ultrawide-bandgap (UWBG) semiconductor owing to its wide bandgap (∼4.4–5.1 eV), ambipolar doping potential, and high theoretical thermal conductivity. However, experimental data on the thermal conductivity of r-GeO2 epitaxial layers have not been reported, primarily due to challenges in phase control and surface roughness. Here, we report a high thermal conductivity of 52.9 ± 6.6 W m−1 K−1 for high-quality (002) r-GeO2 films grown by metal-organic chemical vapor deposition and characterized using time-domain thermoreflectance. The phase control was achieved through a seed-driven stepwise crystallization approach, and the surface roughness was significantly reduced from 76 to 16 nm (locally as low as 1 Å) via chemical mechanical polishing. These results highlight the promise of r-GeO2 as a UWBG oxide platform for power electronics applications.