In this work, we study the thermal transport at β-Ga2O3/metal interfaces, which play important roles in heat dissipation and as electrical contacts in β-Ga2O3 devices. A theoretical Landauer approach was used to model and elucidate the factors that impact the thermal transport at these interfaces. Experimental measurements using time-domain thermoreflectance (TDTR) provided data for the thermal boundary conductance (TBC) between β-Ga2O3 and a range of metals used to create both Schottky and ohmic electrical contacts. From the modeling and experiments, the relation between the metal cutoff frequency and the corresponding TBC is observed. Moreover, the effect of the metal cutoff frequency on TBC is seen as the most significant factor followed by chemical reactions and defects between the metal and the β-Ga2O3. Among all β-Ga2O3/metal interfaces, for Schottky contacts, Ni/β-Ga2O3 interfaces show the highest TBC, while for ohmic contacts, Cr/β-Ga2O3 interfaces show the highest TBC. While there is a clear correlation between TBC and the phonon cutoff frequency of metal contacts, it is also important to control the chemical reactions and other defects at interfaces to maximize the TBC in this system.
Keywords: gallium oxide; interface; metal/β-Ga2O3; thermal boundary conductance; thermal management; time-domain thermoreflectance.