Characterization of the Thermal Boundary Resistance of a Ga2O3/4H-SiC Composite Wafer

The β-gallium oxide (Ga
2
O
3
) material system offers the potential to dramatically improve the electrical performance and cost-effectiveness of next-generation power electronics. This is because of its ultra-wide bandgap (~4.8 eV) and the availability of high-quality single-crystal bulk substrates. However, the low thermal conductivity of Ga
2
O
3
(11-27 W/m-K) implies that significant thermal challenges need to be overcome to commercialize Ga
2
O
3
devices. In the present work, a single crystal (010) Ga
2
O
3
wafer was integrated with a 4H-SiC substrate via fusion bonding to address this concern of poor thermal conductivity. A differential steady-state thermoreflectance method was established to measure the thermal boundary resistance at the Ga
2
O
3
/SiC interface (100 m
²
K/GW), which has yet to be reported due to the limited probing depth of conventional frequency- and time-domain thermoreflectance techniques.