Thermal effects in Ga₂O₃ rectifiers and MOSFETs borrowing from GaN

Ga2O3 is attracting attention for its high critical electric breakdown field and UV/solar-blind photodetection properties. A major limitation to its use in power electronics is the low thermal conductivity, meaning that thermal management issues will need to be addressed in an effective manner. The peak power density of Ga2O3 devices is limited by a hierarchy of thermal resistances from the junction to the ambient. The thermal conductivity at 150°C of Ga2O3 is 15W/mK and anisotropic, compared to the isotropic values for Si of 92W/mK (Ga2O3 is 84% lower) and SiC of 210W/mK (Ga2O3 is 93% lower). Ga2O3 has 12% higher thermal resistance compared to SiC (at 10,000W/m2 K). However, borrowing from technologies developed for GaN electronics, results in the literature indicate a pathway to power dense, low cost, high performance, and reliable Ga2O3-based power modules. In this chapter, we review the current state-of-the-art and detail electrically and thermally driven degradation mechanisms in the most promising Ga2O3 device technologies, namely Schottky rectifiers and metal-oxide-semiconductor field effect transistors. There have been a number of reports of different cooling strategies, with a double side cooling approach combined with a heat spreader used in the active region of the device being able to suppress the device thermal resistance. To achieve the ultimate cooling limits for Ga2O3 devices, issues such as junction-to fluid cooling enabled by advanced thermal management technologies, including Ga2O3–diamond composites, engineering of near-junction resistances and extreme flux convection, nanoengineered heat sinks are needed. With effective thermal management techniques, it may be possible for Ga2O3 electronics to out-perform GaN and SiC in specific applications.