High thermal conductivity of rutile-GeO$_2$ films grown by MOCVD: $52.9~\mathrm{W\,m^{-1}\,K^{-1}}$

TL;DR

This study reports the first experimental measurement of high thermal conductivity in epitaxial rutile-GeO₂ films grown by MOCVD, demonstrating their potential for power electronics due to excellent thermal properties.

Contribution

The paper presents the successful growth and characterization of high-quality rutile-GeO₂ films with record thermal conductivity using a novel seed-driven crystallization method.

Findings

Thermal conductivity of 52.9 W/m·K measured for r-GeO₂ films.

Surface roughness reduced to 16 nm via chemical mechanical polishing.

Phase control achieved through seed-driven stepwise crystallization.

Abstract

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 (MOCVD) and characterized using time-domain thermoreflectance (TDTR). The phase control was achieved through a seed-driven stepwise crystallization (SDSC) approach, and the surface roughness was significantly reduced from 76 nm to 16 nm (locally as low as 1 A) via chemical mechanical polishing (CMP). These results highlight the promise of r-GeO2 as a UWBG oxide platform for power electronics applications.