Thermal Transport Properties of -Ga₂O₃ Thin Films on Si and SiC Substrates Fabricated by an Ion-Cutting Process

Integrating beta-Ga2O3 films onto a highly thermally conductive substrate is regarded as a promising method to remove the heat from beta-Ga2O3 high-power devices, ultimately increasing their reliability and performance. In this work, we fabricated three wafer-scale heterogeneous integration materials (HIMs), i.e., beta-Ga2O3-SiC (GaOSiC), beta-Ga2O3-Al2O3-SiC (GaOISiC), and beta-Ga2O3-Al2O3-Si (GaOISi), by using ion-cutting and surface-activated bonding techniques. The heat block effect of the intermediate amorphous Al2O3 layer from beta-Ga2O3 to SiC is significantly relieved by employing a post-annealing process. Furthermore, the Al2O3 layer blocks the interfusion of elements between beta-Ga2O3 and the host substrate, avoiding the degradation of thermal conductivity of beta-Ga2O3 films after post-annealing. Benefited from this, a relatively high thermal conductivity (9.3 W/mK) is achieved among beta-Ga2O3 thin films with the same thickness and the effective thermal boundary conductance was improved in all beta-Ga2O3 HIMs. One to two orders of magnitude reduction in the junction-to-package device thermal resistance is revealed by the thermal modeling of beta-Ga2O3 HIM metal-oxide-semiconductor field-effect transistors, which demonstrates that extremely high heat dissipation can be realized by optimizing the TBReff value and integrating with thermally conductive substrates (SiC and diamond). These results give key guidelines to engineer the thermal transport properties of beta-Ga2O3 HIMs for device thermal management.